九个PHP很有用功能

Super_Green 发表于 2011-12-22 08:54

<DIV>
<P>下面是九个PHP中很有用的功能，不知道你用过了吗？</P>
<SPAN>1. 函数的任意数目的参数</SPAN>
<P>你可能知道PHP允许你定义一个默认参数的函数。但你可能并不知道PHP还允许你定义一个完全任意的参数的函数</P>
<P>下面是一个示例向你展示了默认参数的函数：</P>
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<DIV class="line number1 index0 alt2">// 两个默认参数的函数 </DIV>
<DIV class="line number2 index1 alt1">function foo($arg1 = '', $arg2 = '') { </DIV>
<DIV class="line number3 index2 alt2">  </DIV>
<DIV class="line number4 index3 alt1">    echo "arg1: $arg1\n"; </DIV>
<DIV class="line number5 index4 alt2">    echo "arg2: $arg2\n"; </DIV>
<DIV class="line number6 index5 alt1">  </DIV>
<DIV class="line number7 index6 alt2">} </DIV>
<DIV class="line number8 index7 alt1">  </DIV>
<DIV class="line number9 index8 alt2">foo('hello','world'); </DIV>
<DIV class="line number10 index9 alt1">/* 输出: </DIV>
<DIV class="line number11 index10 alt2">arg1: hello </DIV>
<DIV class="line number12 index11 alt1">arg2: world </DIV>
<DIV class="line number13 index12 alt2">*/</DIV>
<DIV class="line number14 index13 alt1">  </DIV>
<DIV class="line number15 index14 alt2">foo(); </DIV>
<DIV class="line number16 index15 alt1">/* 输出: </DIV>
<DIV class="line number17 index16 alt2">arg1: </DIV>
<DIV class="line number18 index17 alt1">arg2: </DIV>
<DIV class="line number19 index18 alt2">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>现在我们来看一看一个不定参数的函数，其使用到了?<a href="http://us2.php.net/manual/en/function.func-get-args.php" target="_blank">func_get_args()</A>方法：<BR><SPAN id=more-2394></SPAN></P>
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<DIV class="line number1 index0 alt2">// 是的，形参列表为空 </DIV>
<DIV class="line number2 index1 alt1">function foo() { </DIV>
<DIV class="line number3 index2 alt2">  </DIV>
<DIV class="line number4 index3 alt1">    // 取得所有的传入参数的数组 </DIV>
<DIV class="line number5 index4 alt2">    $args = func_get_args(); </DIV>
<DIV class="line number6 index5 alt1">  </DIV>
<DIV class="line number7 index6 alt2">    foreach ($args as $k => $v) { </DIV>
<DIV class="line number8 index7 alt1">        echo "arg".($k+1).": $v\n"; </DIV>
<DIV class="line number9 index8 alt2">    } </DIV>
<DIV class="line number10 index9 alt1">  </DIV>
<DIV class="line number11 index10 alt2">} </DIV>
<DIV class="line number12 index11 alt1">  </DIV>
<DIV class="line number13 index12 alt2">foo(); </DIV>
<DIV class="line number14 index13 alt1">/* 什么也不会输出 */</DIV>
<DIV class="line number15 index14 alt2">  </DIV>
<DIV class="line number16 index15 alt1">foo('hello'); </DIV>
<DIV class="line number17 index16 alt2">/* 输出 </DIV>
<DIV class="line number18 index17 alt1">arg1: hello </DIV>
<DIV class="line number19 index18 alt2">*/</DIV>
<DIV class="line number20 index19 alt1">  </DIV>
<DIV class="line number21 index20 alt2">foo('hello', 'world', 'again'); </DIV>
<DIV class="line number22 index21 alt1">/* 输出 </DIV>
<DIV class="line number23 index22 alt2">arg1: hello </DIV>
<DIV class="line number24 index23 alt1">arg2: world </DIV>
<DIV class="line number25 index24 alt2">arg3: again </DIV>
<DIV class="line number26 index25 alt1">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<SPAN>2. </SPAN>使用 Glob() 查找文件
<P>很多PHP的函数都有一个比较长的自解释的函数名，但是，当你看到?<a href="http://us.php.net/manual/en/function.glob.php" target="_blank">glob()</A> 的时候，你可能并不知道这个函数是用来干什么的，除非你对它已经很熟悉了。</P>
<P>你可以认为这个函数就好?<a href="http://php.net/manual/en/function.scandir.php" target="_blank">scandir()</A> 一样，其可以用来查找文件。</P>
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<DIV class="line number1 index0 alt2">// 取得所有的后缀为PHP的文件 </DIV>
<DIV class="line number2 index1 alt1">$files = glob('*.php'); </DIV>
<DIV class="line number3 index2 alt2">  </DIV>
<DIV class="line number4 index3 alt1">print_r($files); </DIV>
<DIV class="line number5 index4 alt2">/* 输出: </DIV>
<DIV class="line number6 index5 alt1">Array </DIV>
<DIV class="line number7 index6 alt2">( </DIV>
<DIV class="line number8 index7 alt1">     => phptest.php </DIV>
<DIV class="line number9 index8 alt2">     => pi.php </DIV>
<DIV class="line number10 index9 alt1">     => post_output.php </DIV>
<DIV class="line number11 index10 alt2">     => test.php </DIV>
<DIV class="line number12 index11 alt1">) </DIV>
<DIV class="line number13 index12 alt2">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>你还可以查找多种后缀名</P>
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<DIV class="line number1 index0 alt2">// 取PHP文件和TXT文件 </DIV>
<DIV class="line number2 index1 alt1">$files = glob('*.{php,txt}', GLOB_BRACE); </DIV>
<DIV class="line number3 index2 alt2">  </DIV>
<DIV class="line number4 index3 alt1">print_r($files); </DIV>
<DIV class="line number5 index4 alt2">/* 输出: </DIV>
<DIV class="line number6 index5 alt1">Array </DIV>
<DIV class="line number7 index6 alt2">( </DIV>
<DIV class="line number8 index7 alt1">     => phptest.php </DIV>
<DIV class="line number9 index8 alt2">     => pi.php </DIV>
<DIV class="line number10 index9 alt1">     => post_output.php </DIV>
<DIV class="line number11 index10 alt2">     => test.php </DIV>
<DIV class="line number12 index11 alt1">     => log.txt </DIV>
<DIV class="line number13 index12 alt2">     => test.txt </DIV>
<DIV class="line number14 index13 alt1">) </DIV>
<DIV class="line number15 index14 alt2">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>你还可以加上路径：</P>
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<DIV class="line number1 index0 alt2">$files = glob('../images/a*.jpg'); </DIV>
<DIV class="line number2 index1 alt1">  </DIV>
<DIV class="line number3 index2 alt2">print_r($files); </DIV>
<DIV class="line number4 index3 alt1">/* 输出: </DIV>
<DIV class="line number5 index4 alt2">Array </DIV>
<DIV class="line number6 index5 alt1">( </DIV>
<DIV class="line number7 index6 alt2">     => ../images/apple.jpg </DIV>
<DIV class="line number8 index7 alt1">     => ../images/art.jpg </DIV>
<DIV class="line number9 index8 alt2">) </DIV>
<DIV class="line number10 index9 alt1">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>如果你想得到绝对路径，你可以调用?<a href="http://php.net/manual/en/function.realpath.php" target="_blank">realpath()</A> 函数：</P>
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<DIV class="line number1 index0 alt2">$files = glob('../images/a*.jpg'); </DIV>
<DIV class="line number2 index1 alt1">  </DIV>
<DIV class="line number3 index2 alt2">// applies the function to each array element </DIV>
<DIV class="line number4 index3 alt1">$files = array_map('realpath',$files); </DIV>
<DIV class="line number5 index4 alt2">  </DIV>
<DIV class="line number6 index5 alt1">print_r($files); </DIV>
<DIV class="line number7 index6 alt2">/* output looks like: </DIV>
<DIV class="line number8 index7 alt1">Array </DIV>
<DIV class="line number9 index8 alt2">( </DIV>
<DIV class="line number10 index9 alt1">     => C:\wamp\www\images\apple.jpg </DIV>
<DIV class="line number11 index10 alt2">     => C:\wamp\www\images\art.jpg </DIV>
<DIV class="line number12 index11 alt1">) </DIV>
<DIV class="line number13 index12 alt2">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<SPAN>3. </SPAN>内存使用信息
<P>观察你程序的内存使用能够让你更好的优化你的代码。</P>
<P>PHP 是有垃圾回收机制的，而且有一套很复杂的内存管理机制。你可以知道你的脚本所使用的内存情况。要知道当前内存使用情况，你可以使用?<a href="http://us2.php.net/manual/en/function.memory-get-usage.php" target="_blank">memory_get_usage()</A> 函数，如果你想知道使用内存的峰值，你可以调用<a href="http://us2.php.net/manual/en/function.memory-get-peak-usage.php" target="_blank">memory_get_peak_usage()</A> 函数。</P>
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<DIV class="line number1 index0 alt2">echo "Initial: ".memory_get_usage()." bytes \n"; </DIV>
<DIV class="line number2 index1 alt1">/* 输出 </DIV>
<DIV class="line number3 index2 alt2">Initial: 361400 bytes </DIV>
<DIV class="line number4 index3 alt1">*/</DIV>
<DIV class="line number5 index4 alt2">  </DIV>
<DIV class="line number6 index5 alt1">// 使用内存 </DIV>
<DIV class="line number7 index6 alt2">for ($i = 0; $i < 100000; $i++) { </DIV>
<DIV class="line number8 index7 alt1">    $array []= md5($i); </DIV>
<DIV class="line number9 index8 alt2">} </DIV>
<DIV class="line number10 index9 alt1">  </DIV>
<DIV class="line number11 index10 alt2">// 删除一半的内存 </DIV>
<DIV class="line number12 index11 alt1">for ($i = 0; $i < 100000; $i++) { </DIV>
<DIV class="line number13 index12 alt2">    unset($array[$i]); </DIV>
<DIV class="line number14 index13 alt1">} </DIV>
<DIV class="line number15 index14 alt2">  </DIV>
<DIV class="line number16 index15 alt1">echo "Final: ".memory_get_usage()." bytes \n"; </DIV>
<DIV class="line number17 index16 alt2">/* prints </DIV>
<DIV class="line number18 index17 alt1">Final: 885912 bytes </DIV>
<DIV class="line number19 index18 alt2">*/</DIV>
<DIV class="line number20 index19 alt1">  </DIV>
<DIV class="line number21 index20 alt2">echo "Peak: ".memory_get_peak_usage()." bytes \n"; </DIV>
<DIV class="line number22 index21 alt1">/* 输出峰值 </DIV>
<DIV class="line number23 index22 alt2">Peak: 13687072 bytes </DIV>
<DIV class="line number24 index23 alt1">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<SPAN>4. </SPAN>CPU使用信息
<P>使用?<a href="http://us2.php.net/manual/en/function.getrusage.php" target="_blank">getrusage()</A> 函数可以让你知道CPU的使用情况。注意，这个功能在Windows下不可用。</P>
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<DIV class=container>
<DIV class="line number1 index0 alt2">print_r(getrusage()); </DIV>
<DIV class="line number2 index1 alt1">/* 输出 </DIV>
<DIV class="line number3 index2 alt2">Array </DIV>
<DIV class="line number4 index3 alt1">( </DIV>
<DIV class="line number5 index4 alt2">     => 0 </DIV>
<DIV class="line number6 index5 alt1">     => 0 </DIV>
<DIV class="line number7 index6 alt2">     => 2 </DIV>
<DIV class="line number8 index7 alt1">     => 3 </DIV>
<DIV class="line number9 index8 alt2">     => 12692 </DIV>
<DIV class="line number10 index9 alt1">     => 764 </DIV>
<DIV class="line number11 index10 alt2">     => 3864 </DIV>
<DIV class="line number12 index11 alt1">     => 94 </DIV>
<DIV class="line number13 index12 alt2">     => 0 </DIV>
<DIV class="line number14 index13 alt1">     => 1 </DIV>
<DIV class="line number15 index14 alt2">     => 67 </DIV>
<DIV class="line number16 index15 alt1">     => 4 </DIV>
<DIV class="line number17 index16 alt2">     => 0 </DIV>
<DIV class="line number18 index17 alt1">     => 0 </DIV>
<DIV class="line number19 index18 alt2">     => 0 </DIV>
<DIV class="line number20 index19 alt1">     => 6269 </DIV>
<DIV class="line number21 index20 alt2">     => 0 </DIV>
<DIV class="line number22 index21 alt1">) </DIV>
<DIV class="line number23 index22 alt2">  </DIV>
<DIV class="line number24 index23 alt1">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>这个结构看上出很晦涩，除非你对CPU很了解。下面一些解释：</P>
<UL>
<LI>ru_oublock: 块输出操作
<LI>ru_inblock: 块输入操作
<LI>ru_msgsnd: 发送的message
<LI>ru_msgrcv: 收到的message
<LI>ru_maxrss: 最大驻留集大小
<LI>ru_ixrss: 全部共享内存大小
<LI>ru_idrss:全部非共享内存大小
<LI>ru_minflt: 页回收
<LI>ru_majflt: 页失效
<LI>ru_nsignals: 收到的信号
<LI>ru_nvcsw: 主动上下文切换
<LI>ru_nivcsw: 被动上下文切换
<LI>ru_nswap: 交换区
<LI>ru_utime.tv_usec: 用户态时间 (microseconds)
<LI>ru_utime.tv_sec: 用户态时间(seconds)
<LI>ru_stime.tv_usec: 系统内核时间 (microseconds)
<LI>ru_stime.tv_sec: 系统内核时间?(seconds) </LI></UL>
<P>要看到你的脚本消耗了多少CPU，我们需要看看“用户态的时间”和“系统内核时间”的值。秒和微秒部分是分别提供的，您可以把微秒值除以100万，并把它添加到秒的值后，可以得到有小数部分的秒数。</P>
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<DIV class="line number8 index7 alt1">8</DIV>
<DIV class="line number9 index8 alt2">9</DIV>
<DIV class="line number10 index9 alt1">10</DIV>
<DIV class="line number11 index10 alt2">11</DIV>
<DIV class="line number12 index11 alt1">12</DIV>
<DIV class="line number13 index12 alt2">13</DIV>
<DIV class="line number14 index13 alt1">14</DIV>
<DIV class="line number15 index14 alt2">15</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">// sleep for 3 seconds (non-busy) </DIV>
<DIV class="line number2 index1 alt1">sleep(3); </DIV>
<DIV class="line number3 index2 alt2">  </DIV>
<DIV class="line number4 index3 alt1">$data = getrusage(); </DIV>
<DIV class="line number5 index4 alt2">echo "User time: ". </DIV>
<DIV class="line number6 index5 alt1">    ($data['ru_utime.tv_sec'] + </DIV>
<DIV class="line number7 index6 alt2">    $data['ru_utime.tv_usec'] / 1000000); </DIV>
<DIV class="line number8 index7 alt1">echo "System time: ". </DIV>
<DIV class="line number9 index8 alt2">    ($data['ru_stime.tv_sec'] + </DIV>
<DIV class="line number10 index9 alt1">    $data['ru_stime.tv_usec'] / 1000000); </DIV>
<DIV class="line number11 index10 alt2">  </DIV>
<DIV class="line number12 index11 alt1">/* 输出 </DIV>
<DIV class="line number13 index12 alt2">User time: 0.011552 </DIV>
<DIV class="line number14 index13 alt1">System time: 0 </DIV>
<DIV class="line number15 index14 alt2">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>sleep是不占用系统时间的，我们可以来看下面的一个例子：</P>
<DIV>
<DIV id=highlighter_415966 class="syntaxhighlighterphp ie">
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD class=gutter>
<DIV class="line number1 index0 alt2">1</DIV>
<DIV class="line number2 index1 alt1">2</DIV>
<DIV class="line number3 index2 alt2">3</DIV>
<DIV class="line number4 index3 alt1">4</DIV>
<DIV class="line number5 index4 alt2">5</DIV>
<DIV class="line number6 index5 alt1">6</DIV>
<DIV class="line number7 index6 alt2">7</DIV>
<DIV class="line number8 index7 alt1">8</DIV>
<DIV class="line number9 index8 alt2">9</DIV>
<DIV class="line number10 index9 alt1">10</DIV>
<DIV class="line number11 index10 alt2">11</DIV>
<DIV class="line number12 index11 alt1">12</DIV>
<DIV class="line number13 index12 alt2">13</DIV>
<DIV class="line number14 index13 alt1">14</DIV>
<DIV class="line number15 index14 alt2">15</DIV>
<DIV class="line number16 index15 alt1">16</DIV>
<DIV class="line number17 index16 alt2">17</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">// loop 10 million times (busy) </DIV>
<DIV class="line number2 index1 alt1">for($i=0;$i<10000000;$i++) { </DIV>
<DIV class="line number3 index2 alt2">  </DIV>
<DIV class="line number4 index3 alt1">} </DIV>
<DIV class="line number5 index4 alt2">  </DIV>
<DIV class="line number6 index5 alt1">$data = getrusage(); </DIV>
<DIV class="line number7 index6 alt2">echo "User time: ". </DIV>
<DIV class="line number8 index7 alt1">    ($data['ru_utime.tv_sec'] + </DIV>
<DIV class="line number9 index8 alt2">    $data['ru_utime.tv_usec'] / 1000000); </DIV>
<DIV class="line number10 index9 alt1">echo "System time: ". </DIV>
<DIV class="line number11 index10 alt2">    ($data['ru_stime.tv_sec'] + </DIV>
<DIV class="line number12 index11 alt1">    $data['ru_stime.tv_usec'] / 1000000); </DIV>
<DIV class="line number13 index12 alt2">  </DIV>
<DIV class="line number14 index13 alt1">/* 输出 </DIV>
<DIV class="line number15 index14 alt2">User time: 1.424592 </DIV>
<DIV class="line number16 index15 alt1">System time: 0.004204 </DIV>
<DIV class="line number17 index16 alt2">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>这花了大约14秒的CPU时间，几乎所有的都是用户的时间，因为没有系统调用。</P>
<P>系统时间是CPU花费在系统调用上的上执行内核指令的时间。下面是一个例子：</P>
<DIV>
<DIV id=highlighter_302313 class="syntaxhighlighterphp ie">
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD class=gutter>
<DIV class="line number1 index0 alt2">1</DIV>
<DIV class="line number2 index1 alt1">2</DIV>
<DIV class="line number3 index2 alt2">3</DIV>
<DIV class="line number4 index3 alt1">4</DIV>
<DIV class="line number5 index4 alt2">5</DIV>
<DIV class="line number6 index5 alt1">6</DIV>
<DIV class="line number7 index6 alt2">7</DIV>
<DIV class="line number8 index7 alt1">8</DIV>
<DIV class="line number9 index8 alt2">9</DIV>
<DIV class="line number10 index9 alt1">10</DIV>
<DIV class="line number11 index10 alt2">11</DIV>
<DIV class="line number12 index11 alt1">12</DIV>
<DIV class="line number13 index12 alt2">13</DIV>
<DIV class="line number14 index13 alt1">14</DIV>
<DIV class="line number15 index14 alt2">15</DIV>
<DIV class="line number16 index15 alt1">16</DIV>
<DIV class="line number17 index16 alt2">17</DIV>
<DIV class="line number18 index17 alt1">18</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">$start = microtime(true); </DIV>
<DIV class="line number2 index1 alt1">// keep calling microtime for about 3 seconds </DIV>
<DIV class="line number3 index2 alt2">while(microtime(true) - $start < 3) { </DIV>
<DIV class="line number4 index3 alt1">  </DIV>
<DIV class="line number5 index4 alt2">} </DIV>
<DIV class="line number6 index5 alt1">  </DIV>
<DIV class="line number7 index6 alt2">$data = getrusage(); </DIV>
<DIV class="line number8 index7 alt1">echo "User time: ". </DIV>
<DIV class="line number9 index8 alt2">    ($data['ru_utime.tv_sec'] + </DIV>
<DIV class="line number10 index9 alt1">    $data['ru_utime.tv_usec'] / 1000000); </DIV>
<DIV class="line number11 index10 alt2">echo "System time: ". </DIV>
<DIV class="line number12 index11 alt1">    ($data['ru_stime.tv_sec'] + </DIV>
<DIV class="line number13 index12 alt2">    $data['ru_stime.tv_usec'] / 1000000); </DIV>
<DIV class="line number14 index13 alt1">  </DIV>
<DIV class="line number15 index14 alt2">/* prints </DIV>
<DIV class="line number16 index15 alt1">User time: 1.088171 </DIV>
<DIV class="line number17 index16 alt2">System time: 1.675315 </DIV>
<DIV class="line number18 index17 alt1">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>我们可以看到上面这个例子更耗CPU。</P>
<SPAN>5. </SPAN>系统常量
<P>PHP 提供非常有用的<a href="http://php.net/manual/en/language.constants.predefined.php" target="_blank">系统常量</A> 可以让你得到当前的行号 (__LINE__)，文件 (__FILE__)，目录 (__DIR__)，函数名 (__FUNCTION__)，类名(__CLASS__)，方法名(__METHOD__) 和名字空间 (__NAMESPACE__)，很像C语言。</P>
<P>我们可以以为这些东西主要是用于调试，当也不一定，比如我们可以在include其它文件的时候使用?__FILE__ (当然，你也可以在 PHP 5.3以后使用 __DIR__ )，下面是一个例子。</P>
<DIV>
<DIV id=highlighter_748922 class="syntaxhighlighterphp ie">
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD class=gutter>
<DIV class="line number1 index0 alt2">1</DIV>
<DIV class="line number2 index1 alt1">2</DIV>
<DIV class="line number3 index2 alt2">3</DIV>
<DIV class="line number4 index3 alt1">4</DIV>
<DIV class="line number5 index4 alt2">5</DIV>
<DIV class="line number6 index5 alt1">6</DIV>
<DIV class="line number7 index6 alt2">7</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">// this is relative to the loaded script's path </DIV>
<DIV class="line number2 index1 alt1">// it may cause problems when running scripts from different directories </DIV>
<DIV class="line number3 index2 alt2">require_once('config/database.php'); </DIV>
<DIV class="line number4 index3 alt1">  </DIV>
<DIV class="line number5 index4 alt2">// this is always relative to this file's path </DIV>
<DIV class="line number6 index5 alt1">// no matter where it was included from </DIV>
<DIV class="line number7 index6 alt2">require_once(dirname(__FILE__) . '/config/database.php');</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>下面是使用 __LINE__ 来输出一些debug的信息，这样有助于你调试程序：</P>
<DIV>
<DIV id=highlighter_227503 class="syntaxhighlighterphp ie">
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD class=gutter>
<DIV class="line number1 index0 alt2">1</DIV>
<DIV class="line number2 index1 alt1">2</DIV>
<DIV class="line number3 index2 alt2">3</DIV>
<DIV class="line number4 index3 alt1">4</DIV>
<DIV class="line number5 index4 alt2">5</DIV>
<DIV class="line number6 index5 alt1">6</DIV>
<DIV class="line number7 index6 alt2">7</DIV>
<DIV class="line number8 index7 alt1">8</DIV>
<DIV class="line number9 index8 alt2">9</DIV>
<DIV class="line number10 index9 alt1">10</DIV>
<DIV class="line number11 index10 alt2">11</DIV>
<DIV class="line number12 index11 alt1">12</DIV>
<DIV class="line number13 index12 alt2">13</DIV>
<DIV class="line number14 index13 alt1">14</DIV>
<DIV class="line number15 index14 alt2">15</DIV>
<DIV class="line number16 index15 alt1">16</DIV>
<DIV class="line number17 index16 alt2">17</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">// some code </DIV>
<DIV class="line number2 index1 alt1">// ... </DIV>
<DIV class="line number3 index2 alt2">my_debug("some debug message", __LINE__); </DIV>
<DIV class="line number4 index3 alt1">/* 输出 </DIV>
<DIV class="line number5 index4 alt2">Line 4: some debug message </DIV>
<DIV class="line number6 index5 alt1">*/</DIV>
<DIV class="line number7 index6 alt2">  </DIV>
<DIV class="line number8 index7 alt1">// some more code </DIV>
<DIV class="line number9 index8 alt2">// ... </DIV>
<DIV class="line number10 index9 alt1">my_debug("another debug message", __LINE__); </DIV>
<DIV class="line number11 index10 alt2">/* 输出 </DIV>
<DIV class="line number12 index11 alt1">Line 11: another debug message </DIV>
<DIV class="line number13 index12 alt2">*/</DIV>
<DIV class="line number14 index13 alt1">  </DIV>
<DIV class="line number15 index14 alt2">function my_debug($msg, $line) { </DIV>
<DIV class="line number16 index15 alt1">    echo "Line $line: $msg\n"; </DIV>
<DIV class="line number17 index16 alt2">}</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<SPAN>6.生成唯一的ID</SPAN>
<P>有很多人使用 md5() 来生成一个唯一的ID，如下所示：</P>
<DIV>
<DIV id=highlighter_869861 class="syntaxhighlighterphp ie">
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD class=gutter>
<DIV class="line number1 index0 alt2">1</DIV>
<DIV class="line number2 index1 alt1">2</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">// generate unique string </DIV>
<DIV class="line number2 index1 alt1">echo md5(time() . mt_rand(1,1000000));</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>其实，PHP中有一个叫?<a href="http://us2.php.net/manual/en/function.uniqid.php" target="_blank">uniqid()</A> 的函数是专门用来干这个的：</P>
<DIV>
<DIV id=highlighter_270188 class="syntaxhighlighterphp ie">
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD class=gutter>
<DIV class="line number1 index0 alt2">1</DIV>
<DIV class="line number2 index1 alt1">2</DIV>
<DIV class="line number3 index2 alt2">3</DIV>
<DIV class="line number4 index3 alt1">4</DIV>
<DIV class="line number5 index4 alt2">5</DIV>
<DIV class="line number6 index5 alt1">6</DIV>
<DIV class="line number7 index6 alt2">7</DIV>
<DIV class="line number8 index7 alt1">8</DIV>
<DIV class="line number9 index8 alt2">9</DIV>
<DIV class="line number10 index9 alt1">10</DIV>
<DIV class="line number11 index10 alt2">11</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">// generate unique string </DIV>
<DIV class="line number2 index1 alt1">echo uniqid(); </DIV>
<DIV class="line number3 index2 alt2">/* 输出 </DIV>
<DIV class="line number4 index3 alt1">4bd67c947233e </DIV>
<DIV class="line number5 index4 alt2">*/</DIV>
<DIV class="line number6 index5 alt1">  </DIV>
<DIV class="line number7 index6 alt2">// generate another unique string </DIV>
<DIV class="line number8 index7 alt1">echo uniqid(); </DIV>
<DIV class="line number9 index8 alt2">/* 输出 </DIV>
<DIV class="line number10 index9 alt1">4bd67c9472340 </DIV>
<DIV class="line number11 index10 alt2">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>可能你会注意到生成出来的ID前几位是一样的，这是因为生成器依赖于系统的时间，这其实是一个非常不错的功能，因为你是很容易为你的这些ID排序的。这点MD5是做不到的。</P>
<P>你还可以加上前缀避免重名：</P>
<DIV>
<DIV id=highlighter_11954 class="syntaxhighlighterphp ie">
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD class=gutter>
<DIV class="line number1 index0 alt2">1</DIV>
<DIV class="line number2 index1 alt1">2</DIV>
<DIV class="line number3 index2 alt2">3</DIV>
<DIV class="line number4 index3 alt1">4</DIV>
<DIV class="line number5 index4 alt2">5</DIV>
<DIV class="line number6 index5 alt1">6</DIV>
<DIV class="line number7 index6 alt2">7</DIV>
<DIV class="line number8 index7 alt1">8</DIV>
<DIV class="line number9 index8 alt2">9</DIV>
<DIV class="line number10 index9 alt1">10</DIV>
<DIV class="line number11 index10 alt2">11</DIV>
<DIV class="line number12 index11 alt1">12</DIV>
<DIV class="line number13 index12 alt2">13</DIV>
<DIV class="line number14 index13 alt1">14</DIV>
<DIV class="line number15 index14 alt2">15</DIV>
<DIV class="line number16 index15 alt1">16</DIV>
<DIV class="line number17 index16 alt2">17</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">// 前缀 </DIV>
<DIV class="line number2 index1 alt1">echo uniqid('foo_'); </DIV>
<DIV class="line number3 index2 alt2">/* 输出 </DIV>
<DIV class="line number4 index3 alt1">foo_4bd67d6cd8b8f </DIV>
<DIV class="line number5 index4 alt2">*/</DIV>
<DIV class="line number6 index5 alt1">  </DIV>
<DIV class="line number7 index6 alt2">// 有更多的熵 </DIV>
<DIV class="line number8 index7 alt1">echo uniqid('',true); </DIV>
<DIV class="line number9 index8 alt2">/* 输出 </DIV>
<DIV class="line number10 index9 alt1">4bd67d6cd8b926.12135106 </DIV>
<DIV class="line number11 index10 alt2">*/</DIV>
<DIV class="line number12 index11 alt1">  </DIV>
<DIV class="line number13 index12 alt2">// 都有 </DIV>
<DIV class="line number14 index13 alt1">echo uniqid('bar_',true); </DIV>
<DIV class="line number15 index14 alt2">/* 输出 </DIV>
<DIV class="line number16 index15 alt1">bar_4bd67da367b650.43684647 </DIV>
<DIV class="line number17 index16 alt2">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>而且，生成出来的ID会比MD5生成的要短，这会让你节省很多空间。</P>
<SPAN>7. </SPAN>序列化
<P>你是否会把一个比较复杂的数据结构存到数据库或是文件中？你并不需要自己去写自己的算法。PHP早已为你做好了，其提供了两个函数：?<a href="http://php.net/manual/en/function.serialize.php" target="_blank">serialize()</A> 和 <a href="http://www.php.net/manual/en/function.unserialize.php" target="_blank">unserialize()</A>:</P>
<DIV>
<DIV id=highlighter_319432 class="syntaxhighlighterphp ie">
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD class=gutter>
<DIV class="line number1 index0 alt2">1</DIV>
<DIV class="line number2 index1 alt1">2</DIV>
<DIV class="line number3 index2 alt2">3</DIV>
<DIV class="line number4 index3 alt1">4</DIV>
<DIV class="line number5 index4 alt2">5</DIV>
<DIV class="line number6 index5 alt1">6</DIV>
<DIV class="line number7 index6 alt2">7</DIV>
<DIV class="line number8 index7 alt1">8</DIV>
<DIV class="line number9 index8 alt2">9</DIV>
<DIV class="line number10 index9 alt1">10</DIV>
<DIV class="line number11 index10 alt2">11</DIV>
<DIV class="line number12 index11 alt1">12</DIV>
<DIV class="line number13 index12 alt2">13</DIV>
<DIV class="line number14 index13 alt1">14</DIV>
<DIV class="line number15 index14 alt2">15</DIV>
<DIV class="line number16 index15 alt1">16</DIV>
<DIV class="line number17 index16 alt2">17</DIV>
<DIV class="line number18 index17 alt1">18</DIV>
<DIV class="line number19 index18 alt2">19</DIV>
<DIV class="line number20 index19 alt1">20</DIV>
<DIV class="line number21 index20 alt2">21</DIV>
<DIV class="line number22 index21 alt1">22</DIV>
<DIV class="line number23 index22 alt2">23</DIV>
<DIV class="line number24 index23 alt1">24</DIV>
<DIV class="line number25 index24 alt2">25</DIV>
<DIV class="line number26 index25 alt1">26</DIV>
<DIV class="line number27 index26 alt2">27</DIV>
<DIV class="line number28 index27 alt1">28</DIV>
<DIV class="line number29 index28 alt2">29</DIV>
<DIV class="line number30 index29 alt1">30</DIV>
<DIV class="line number31 index30 alt2">31</DIV>
<DIV class="line number32 index31 alt1">32</DIV>
<DIV class="line number33 index32 alt2">33</DIV>
<DIV class="line number34 index33 alt1">34</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">// 一个复杂的数组 </DIV>
<DIV class="line number2 index1 alt1">$myvar = array( </DIV>
<DIV class="line number3 index2 alt2">    'hello', </DIV>
<DIV class="line number4 index3 alt1">    42, </DIV>
<DIV class="line number5 index4 alt2">    array(1,'two'), </DIV>
<DIV class="line number6 index5 alt1">    'apple'</DIV>
<DIV class="line number7 index6 alt2">); </DIV>
<DIV class="line number8 index7 alt1">  </DIV>
<DIV class="line number9 index8 alt2">// 序列化 </DIV>
<DIV class="line number10 index9 alt1">$string = serialize($myvar); </DIV>
<DIV class="line number11 index10 alt2">  </DIV>
<DIV class="line number12 index11 alt1">echo $string; </DIV>
<DIV class="line number13 index12 alt2">/* 输出 </DIV>
<DIV class="line number14 index13 alt1">a:4:{i:0;s:5:"hello";i:1;i:42;i:2;a:2:{i:0;i:1;i:1;s:3:"two";}i:3;s:5:"apple";} </DIV>
<DIV class="line number15 index14 alt2">*/</DIV>
<DIV class="line number16 index15 alt1">  </DIV>
<DIV class="line number17 index16 alt2">// 反序例化 </DIV>
<DIV class="line number18 index17 alt1">$newvar = unserialize($string); </DIV>
<DIV class="line number19 index18 alt2">  </DIV>
<DIV class="line number20 index19 alt1">print_r($newvar); </DIV>
<DIV class="line number21 index20 alt2">/* 输出 </DIV>
<DIV class="line number22 index21 alt1">Array </DIV>
<DIV class="line number23 index22 alt2">( </DIV>
<DIV class="line number24 index23 alt1">     => hello </DIV>
<DIV class="line number25 index24 alt2">     => 42 </DIV>
<DIV class="line number26 index25 alt1">     => Array </DIV>
<DIV class="line number27 index26 alt2">        ( </DIV>
<DIV class="line number28 index27 alt1">             => 1 </DIV>
<DIV class="line number29 index28 alt2">             => two </DIV>
<DIV class="line number30 index29 alt1">        ) </DIV>
<DIV class="line number31 index30 alt2">  </DIV>
<DIV class="line number32 index31 alt1">     => apple </DIV>
<DIV class="line number33 index32 alt2">) </DIV>
<DIV class="line number34 index33 alt1">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>这是PHP的原生函数，然而在今天JSON越来越流行，所以在PHP5.2以后，PHP开始支持JSON，你可以使用 json_encode() 和 json_decode() 函数</P>
<DIV>
<DIV id=highlighter_793712 class="syntaxhighlighterphp ie">
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD class=gutter>
<DIV class="line number1 index0 alt2">1</DIV>
<DIV class="line number2 index1 alt1">2</DIV>
<DIV class="line number3 index2 alt2">3</DIV>
<DIV class="line number4 index3 alt1">4</DIV>
<DIV class="line number5 index4 alt2">5</DIV>
<DIV class="line number6 index5 alt1">6</DIV>
<DIV class="line number7 index6 alt2">7</DIV>
<DIV class="line number8 index7 alt1">8</DIV>
<DIV class="line number9 index8 alt2">9</DIV>
<DIV class="line number10 index9 alt1">10</DIV>
<DIV class="line number11 index10 alt2">11</DIV>
<DIV class="line number12 index11 alt1">12</DIV>
<DIV class="line number13 index12 alt2">13</DIV>
<DIV class="line number14 index13 alt1">14</DIV>
<DIV class="line number15 index14 alt2">15</DIV>
<DIV class="line number16 index15 alt1">16</DIV>
<DIV class="line number17 index16 alt2">17</DIV>
<DIV class="line number18 index17 alt1">18</DIV>
<DIV class="line number19 index18 alt2">19</DIV>
<DIV class="line number20 index19 alt1">20</DIV>
<DIV class="line number21 index20 alt2">21</DIV>
<DIV class="line number22 index21 alt1">22</DIV>
<DIV class="line number23 index22 alt2">23</DIV>
<DIV class="line number24 index23 alt1">24</DIV>
<DIV class="line number25 index24 alt2">25</DIV>
<DIV class="line number26 index25 alt1">26</DIV>
<DIV class="line number27 index26 alt2">27</DIV>
<DIV class="line number28 index27 alt1">28</DIV>
<DIV class="line number29 index28 alt2">29</DIV>
<DIV class="line number30 index29 alt1">30</DIV>
<DIV class="line number31 index30 alt2">31</DIV>
<DIV class="line number32 index31 alt1">32</DIV>
<DIV class="line number33 index32 alt2">33</DIV>
<DIV class="line number34 index33 alt1">34</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">// a complex array </DIV>
<DIV class="line number2 index1 alt1">$myvar = array( </DIV>
<DIV class="line number3 index2 alt2">    'hello', </DIV>
<DIV class="line number4 index3 alt1">    42, </DIV>
<DIV class="line number5 index4 alt2">    array(1,'two'), </DIV>
<DIV class="line number6 index5 alt1">    'apple'</DIV>
<DIV class="line number7 index6 alt2">); </DIV>
<DIV class="line number8 index7 alt1">  </DIV>
<DIV class="line number9 index8 alt2">// convert to a string </DIV>
<DIV class="line number10 index9 alt1">$string = json_encode($myvar); </DIV>
<DIV class="line number11 index10 alt2">  </DIV>
<DIV class="line number12 index11 alt1">echo $string; </DIV>
<DIV class="line number13 index12 alt2">/* prints </DIV>
<DIV class="line number14 index13 alt1">["hello",42,,"apple"] </DIV>
<DIV class="line number15 index14 alt2">*/</DIV>
<DIV class="line number16 index15 alt1">  </DIV>
<DIV class="line number17 index16 alt2">// you can reproduce the original variable </DIV>
<DIV class="line number18 index17 alt1">$newvar = json_decode($string); </DIV>
<DIV class="line number19 index18 alt2">  </DIV>
<DIV class="line number20 index19 alt1">print_r($newvar); </DIV>
<DIV class="line number21 index20 alt2">/* prints </DIV>
<DIV class="line number22 index21 alt1">Array </DIV>
<DIV class="line number23 index22 alt2">( </DIV>
<DIV class="line number24 index23 alt1">     => hello </DIV>
<DIV class="line number25 index24 alt2">     => 42 </DIV>
<DIV class="line number26 index25 alt1">     => Array </DIV>
<DIV class="line number27 index26 alt2">        ( </DIV>
<DIV class="line number28 index27 alt1">             => 1 </DIV>
<DIV class="line number29 index28 alt2">             => two </DIV>
<DIV class="line number30 index29 alt1">        ) </DIV>
<DIV class="line number31 index30 alt2">  </DIV>
<DIV class="line number32 index31 alt1">     => apple </DIV>
<DIV class="line number33 index32 alt2">) </DIV>
<DIV class="line number34 index33 alt1">*/</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>这看起来更为紧凑一些了，而且还兼容于Javascript和其它语言。但是对于一些非常复杂的数据结构，可能会造成数据丢失。</P>
<SPAN>8. </SPAN>字符串压缩
<P>当我们说到压缩，我们可能会想到文件压缩，其实，字符串也是可以压缩的。PHP提供了?<a href="http://php.net/manual/en/function.gzcompress.php" target="_blank">gzcompress()</A> 和 <a href="http://www.php.net/manual/en/function.gzuncompress.php" target="_blank">gzuncompress()</A> 函数：</P>
<DIV>
<DIV id=highlighter_425530 class="syntaxhighlighterphp ie">
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD class=gutter>
<DIV class="line number1 index0 alt2">1</DIV>
<DIV class="line number2 index1 alt1">2</DIV>
<DIV class="line number3 index2 alt2">3</DIV>
<DIV class="line number4 index3 alt1">4</DIV>
<DIV class="line number5 index4 alt2">5</DIV>
<DIV class="line number6 index5 alt1">6</DIV>
<DIV class="line number7 index6 alt2">7</DIV>
<DIV class="line number8 index7 alt1">8</DIV>
<DIV class="line number9 index8 alt2">9</DIV>
<DIV class="line number10 index9 alt1">10</DIV>
<DIV class="line number11 index10 alt2">11</DIV>
<DIV class="line number12 index11 alt1">12</DIV>
<DIV class="line number13 index12 alt2">13</DIV>
<DIV class="line number14 index13 alt1">14</DIV>
<DIV class="line number15 index14 alt2">15</DIV>
<DIV class="line number16 index15 alt1">16</DIV>
<DIV class="line number17 index16 alt2">17</DIV>
<DIV class="line number18 index17 alt1">18</DIV>
<DIV class="line number19 index18 alt2">19</DIV>
<DIV class="line number20 index19 alt1">20</DIV>
<DIV class="line number21 index20 alt2">21</DIV>
<DIV class="line number22 index21 alt1">22</DIV>
<DIV class="line number23 index22 alt2">23</DIV>
<DIV class="line number24 index23 alt1">24</DIV>
<DIV class="line number25 index24 alt2">25</DIV>
<DIV class="line number26 index25 alt1">26</DIV>
<DIV class="line number27 index26 alt2">27</DIV>
<DIV class="line number28 index27 alt1">28</DIV>
<DIV class="line number29 index28 alt2">29</DIV>
<DIV class="line number30 index29 alt1">30</DIV>
<DIV class="line number31 index30 alt2">31</DIV>
<DIV class="line number32 index31 alt1">32</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">$string = </DIV>
<DIV class="line number2 index1 alt1">"Lorem ipsum dolor sit amet, consectetur </DIV>
<DIV class="line number3 index2 alt2">adipiscing elit. Nunc ut elit id mi ultricies </DIV>
<DIV class="line number4 index3 alt1">adipiscing. Nulla facilisi. Praesent pulvinar, </DIV>
<DIV class="line number5 index4 alt2">sapien vel feugiat vestibulum, nulla dui pretium orci, </DIV>
<DIV class="line number6 index5 alt1">non ultricies elit lacus quis ante. Lorem ipsum dolor </DIV>
<DIV class="line number7 index6 alt2">sit amet, consectetur adipiscing elit. Aliquam </DIV>
<DIV class="line number8 index7 alt1">pretium ullamcorper urna quis iaculis. Etiam ac massa </DIV>
<DIV class="line number9 index8 alt2">sed turpis tempor luctus. Curabitur sed nibh eu elit </DIV>
<DIV class="line number10 index9 alt1">mollis congue. Praesent ipsum diam, consectetur vitae </DIV>
<DIV class="line number11 index10 alt2">ornare a, aliquam a nunc. In id magna pellentesque </DIV>
<DIV class="line number12 index11 alt1">tellus posuere adipiscing. Sed non mi metus, at lacinia </DIV>
<DIV class="line number13 index12 alt2">augue. Sed magna nisi, ornare in mollis in, mollis </DIV>
<DIV class="line number14 index13 alt1">sed nunc. Etiam at justo in leo congue mollis. </DIV>
<DIV class="line number15 index14 alt2">Nullam in neque eget metus hendrerit scelerisque </DIV>
<DIV class="line number16 index15 alt1">eu non enim. Ut malesuada lacus eu nulla bibendum </DIV>
<DIV class="line number17 index16 alt2">id euismod urna sodales. "; </DIV>
<DIV class="line number18 index17 alt1">  </DIV>
<DIV class="line number19 index18 alt2">$compressed = gzcompress($string); </DIV>
<DIV class="line number20 index19 alt1">  </DIV>
<DIV class="line number21 index20 alt2">echo "Original size: ". strlen($string)."\n"; </DIV>
<DIV class="line number22 index21 alt1">/* 输出原始大小 </DIV>
<DIV class="line number23 index22 alt2">Original size: 800 </DIV>
<DIV class="line number24 index23 alt1">*/</DIV>
<DIV class="line number25 index24 alt2">  </DIV>
<DIV class="line number26 index25 alt1">echo "Compressed size: ". strlen($compressed)."\n"; </DIV>
<DIV class="line number27 index26 alt2">/* 输出压缩后的大小 </DIV>
<DIV class="line number28 index27 alt1">Compressed size: 418 </DIV>
<DIV class="line number29 index28 alt2">*/</DIV>
<DIV class="line number30 index29 alt1">  </DIV>
<DIV class="line number31 index30 alt2">// 解压缩 </DIV>
<DIV class="line number32 index31 alt1">$original = gzuncompress($compressed);</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>几乎有<SPAN style="LINE-HEIGHT: 19px; FONT-FAMILY: Georgia, 'Times New Roman', 'Bitstream Charter', Times, serif; WHITE-SPACE: normal; FONT-SIZE: 13px">50% 压缩比率。同时，你还可以使用?<a href="http://www.php.net/manual/en/function.gzencode.php" target="_blank">gzencode()</A> 和 <a href="http://www.php.net/manual/en/function.gzdecode.php" target="_blank">gzdecode()</A> 函数来压缩，只不用其用了不同的压缩算法。</SPAN></P>
<SPAN>9. 注册停止</SPAN>函数
<P>有一个函数叫做?<a href="http://www.php.net/manual/en/function.register-shutdown-function.php" target="_blank">register_shutdown_function()</A>，可以让你在整个脚本停时前运行代码。让我们看下面的一个示例：</P>
<DIV>
<DIV id=highlighter_702397 class="syntaxhighlighterphp ie">
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD class=gutter>
<DIV class="line number1 index0 alt2">1</DIV>
<DIV class="line number2 index1 alt1">2</DIV>
<DIV class="line number3 index2 alt2">3</DIV>
<DIV class="line number4 index3 alt1">4</DIV>
<DIV class="line number5 index4 alt2">5</DIV>
<DIV class="line number6 index5 alt1">6</DIV>
<DIV class="line number7 index6 alt2">7</DIV>
<DIV class="line number8 index7 alt1">8</DIV>
<DIV class="line number9 index8 alt2">9</DIV>
<DIV class="line number10 index9 alt1">10</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">// capture the start time </DIV>
<DIV class="line number2 index1 alt1">$start_time = microtime(true); </DIV>
<DIV class="line number3 index2 alt2">  </DIV>
<DIV class="line number4 index3 alt1">// do some stuff </DIV>
<DIV class="line number5 index4 alt2">// ... </DIV>
<DIV class="line number6 index5 alt1">  </DIV>
<DIV class="line number7 index6 alt2">// display how long the script took </DIV>
<DIV class="line number8 index7 alt1">echo "execution took: ". </DIV>
<DIV class="line number9 index8 alt2">        (microtime(true) - $start_time). </DIV>
<DIV class="line number10 index9 alt1">        " seconds.";</DIV></DIV></TD></TR></TBODY></TABLE></DIV></DIV>
<P>上面这个示例只不过是用来计算某个函数运行的时间。然后，如果你在函数中间调用?<a href="http://php.net/manual/en/function.exit.php" target="_blank">exit()</A> 函数，那么你的最后的代码将不会被运行到。并且，如果该脚本在浏览器终止（用户按停止按钮），其也无法被运行。</P>
<P>而当我们使用了register_shutdown_function()后，你的程序就算是在脚本被停止后也会被运行：</P>
<DIV>
<DIV id=highlighter_532492 class="syntaxhighlighterphp ie">
<TABLE border=0 cellSpacing=0 cellPadding=0>
<TBODY>
<TR>
<TD class=gutter>
<DIV class="line number1 index0 alt2">1</DIV>
<DIV class="line number2 index1 alt1">2</DIV>
<DIV class="line number3 index2 alt2">3</DIV>
<DIV class="line number4 index3 alt1">4</DIV>
<DIV class="line number5 index4 alt2">5</DIV>
<DIV class="line number6 index5 alt1">6</DIV>
<DIV class="line number7 index6 alt2">7</DIV>
<DIV class="line number8 index7 alt1">8</DIV>
<DIV class="line number9 index8 alt2">9</DIV>
<DIV class="line number10 index9 alt1">10</DIV>
<DIV class="line number11 index10 alt2">11</DIV>
<DIV class="line number12 index11 alt1">12</DIV>
<DIV class="line number13 index12 alt2">13</DIV>
<DIV class="line number14 index13 alt1">14</DIV></TD>
<TD class=code>
<DIV class=container>
<DIV class="line number1 index0 alt2">$start_time = microtime(true); </DIV>
<DIV class="line number2 index1 alt1">  </DIV>
<DIV class="line number3 index2 alt2">register_shutdown_function('my_shutdown'); </DIV>
<DIV class="line number4 index3 alt1">  </DIV>
<DIV class="line number5 index4 alt2">// do some stuff </DIV>
<DIV class="line number6 index5 alt1">// ... </DIV>
<DIV class="line number7 index6 alt2">  </DIV>
<DIV class="line number8 index7 alt1">function my_shutdown() { </DIV>
<DIV class="line number9 index8 alt2">    global $start_time; </DIV>
<DIV class="line number10 index9 alt1">  </DIV>
<DIV class="line number11 index10 alt2">    echo "execution took: ". </DIV>
<DIV class="line number12 index11 alt1">            (microtime(true) - $start_time). </DIV>
<DIV class="line number13 index12 alt2">            " seconds."; </DIV>
<DIV class="line number14 index13 alt1">}</DIV></DIV></TD></TR></TBODY></TABLE></DIV>
<DIV class="syntaxhighlighterphp ie">转载：<a href="http://coolshell.cn/articles/2394.html" target="_blank">http://coolshell.cn/articles/2394.html</A></DIV></DIV></DIV>

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Chinaunix's Archiver

九个PHP很有用功能