36计教您如何提高PHP代码质量

作者Silver Moon在 binarytides 上发表的一篇《 40 Techniques to enhance your php code 》，文中主要探讨了如何提高PHP代码质量，供开发者学习与参考。 1.不要使用相对路径 常常会看到: require_once('../../lib/some_class.php'); 该方法有很多缺点: 它首

作者Silver Moon在binarytides上发表的一篇《40+ Techniques to enhance your php code》，文中主要探讨了如何提高PHP代码质量，供开发者学习与参考。

1.不要使用相对路径

常常会看到:

<ol><li><span><span>require_once('../../lib/some_class.php'); </span></span></li></ol>

该方法有很多缺点:

它首先查找指定的php包含路径, 然后查找当前目录.

因此会检查过多路径.

如果该脚本被另一目录的脚本包含, 它的基本目录变成了另一脚本所在的目录.

另一问题, 当定时任务运行该脚本, 它的上级目录可能就不是工作目录了.

因此最佳选择是使用绝对路径:

<ol>
<li><span><span>define('ROOT' , '/var/www/project/');  </span></span></li>
<li><span>require_once(ROOT . '../../lib/some_class.php');  </span></li>
<li><span>       </span></li>
<li><span>//rest of the code </span></li>
</ol>

我们定义了一个绝对路径, 值被写死了. 我们还可以改进它. 路径 /var/www/project 也可能会改变, 那么我们每次都要改变它吗? 不是的, 我们可以使用__FILE__常量, 如:

<ol>
<li><span><span>//suppose your script is /var/www/project/index.php  </span></span></li>
<li><span>//Then __FILE__ will always have that full path.  </span></li>
<li><span>       </span></li>
<li><span>define('ROOT' , pathinfo(__FILE__, PATHINFO_DIRNAME));  </span></li>
<li><span>require_once(ROOT . '../../lib/some_class.php');  </span></li>
<li><span>   </span></li>
<li><span>//rest of the code </span></li>
</ol>

现在, 无论你移到哪个目录, 如移到一个外网的服务器上, 代码无须更改便可正确运行.

2. 不要直接使用 require, include, include_once, required_once

可以在脚本头部引入多个文件, 像类库, 工具文件和助手函数等, 如:

<ol>
<li><span><span>require_once('lib/Database.php');  </span></span></li>
<li><span>require_once('lib/Mail.php');  </span></li>
<li><span>require_once('helpers/utitlity_functions.php'); </span></li>
</ol>

这种用法相当原始. 应该更灵活点. 应编写个助手函数包含文件. 例如:

<ol>
<li><span><span>function load_class($class_name)  </span></span></li>
<li><span>{  </span></li>
<li><span> //path to the class file  </span></li>
<li>
<span> $</span><span>path</span><span> = </span><span>ROOT</span><span> . '/lib/' . $class_name . '.php');  </span>
</li>
<li><span> require_once( $path );  </span></li>
<li><span>}  </span></li>
<li><span>       </span></li>
<li><span>load_class('Database');  </span></li>
<li><span>load_class('Mail'); </span></li>
</ol>

有什么不一样吗? 该代码更具可读性.

將来你可以按需扩展该函数, 如:

<ol>
<li><span><span>function load_class($class_name)  </span></span></li>
<li><span>{  </span></li>
<li><span>  //path to the class file  </span></li>
<li>
<span>    $</span><span>path</span><span> = </span><span>ROOT</span><span> . '/lib/' . $class_name . '.php');  </span>
</li>
<li><span>   </span></li>
<li><span>  if(file_exists($path))  </span></li>
<li><span>    {  </span></li>
<li><span> require_once( $path );  </span></li>
<li><span>        }  </span></li>
<li><span>} </span></li>
</ol>

还可做得更多:

为同样文件查找多个目录

能很容易的改变放置类文件的目录, 无须在代码各处一一修改

可使用类似的函数加载文件, 如html内容.

3. 为应用保留调试代码

在开发环境中, 我们打印数据库查询语句, 转存有问题的变量值, 而一旦问题解决, 我们注释或删除它们. 然而更好的做法是保留调试代码.

在开发环境中, 你可以:

<ol>
<li><span><span>define('ENVIRONMENT' , 'development');  </span></span></li>
<li><span>   </span></li>
<li>
<span>if(! $db-</span><span>></span><span>query( $query )  </span>
</li>
<li><span>{  </span></li>
<li>
<span>   if(</span><span>ENVIRONMENT</span><span> == 'development')  </span>
</li>
<li><span>   {  </span></li>
<li><span>      echo "$query failed";  </span></li>
<li><span>  }  </span></li>
<li><span>   else  </span></li>
<li><span>    {  </span></li>
<li><span>       echo "Database error. Please contact administrator";  </span></li>
<li><span>    }  </span></li>
<li><span>} </span></li>
</ol>

在服务器中, 你可以:

<ol>
<li><span><span>define('ENVIRONMENT' , 'production');  </span></span></li>
<li>
<span>if(! $db-</span><span>></span><span>query( $query )  </span>
</li>
<li><span>{  </span></li>
<li>
<span>   if(</span><span>ENVIRONMENT</span><span> == 'development')  </span>
</li>
<li><span>   {  </span></li>
<li><span>       echo "$query failed";  </span></li>
<li><span>   }  </span></li>
<li><span>    else  </span></li>
<li><span>    {  </span></li>
<li><span>        echo "Database error. Please contact administrator";  </span></li>
<li><span>    }  </span></li>
<li><span>} </span></li>
</ol>

4. 使用可跨平台的函数执行命令

system, exec, passthru, shell_exec 这4个函数可用于执行系统命令. 每个的行为都有细微差别. 问题在于, 当在共享主机中, 某些函数可能被选择性的禁用. 大多数新手趋于每次首先检查哪个函数可用, 然而再使用它.

更好的方案是封成函数一个可跨平台的函数。

<ol>
<li><span><span>01  /**  </span></span></li>
<li><span>02      Method to execute a command in the terminal  </span></li>
<li><span>03      Uses :  </span></li>
<li><span>04     </span></li>
<li><span>05      1. system  </span></li>
<li><span>06      2. passthru  </span></li>
<li><span>07      3. exec  </span></li>
<li><span>08      4. shell_exec  </span></li>
<li><span>09     </span></li>
<li><span>10  */  </span></li>
<li><span>11  function terminal($command)  </span></li>
<li><span>12  {  </span></li>
<li><span>13      //system  </span></li>
<li><span>14      if(function_exists('system'))  </span></li>
<li><span>15      {  </span></li>
<li><span>16          ob_start();  </span></li>
<li><span>17          system($command , $return_var);  </span></li>
<li>
<span>18          $</span><span>output</span><span> = </span><span>ob_get_contents</span><span>();  </span>
</li>
<li><span>19          ob_end_clean();  </span></li>
<li><span>20      }  </span></li>
<li><span>21      //passthru  </span></li>
<li><span>22      else if(function_exists('passthru'))  </span></li>
<li><span>23      {  </span></li>
<li><span>24          ob_start();  </span></li>
<li><span>25          passthru($command , $return_var);  </span></li>
<li>
<span>26          $</span><span>output</span><span> = </span><span>ob_get_contents</span><span>();  </span>
</li>
<li><span>27          ob_end_clean();  </span></li>
<li><span>28      }  </span></li>
<li><span>29     </span></li>
<li><span>30      //exec  </span></li>
<li><span>31      else if(function_exists('exec'))  </span></li>
<li><span>32      {  </span></li>
<li><span>33          exec($command , $output , $return_var);  </span></li>
<li>
<span>34          $</span><span>output</span><span> = </span><span>implode</span><span>("\n" , $output);  </span>
</li>
<li><span>35      }  </span></li>
<li><span>36     </span></li>
<li><span>37      //shell_exec  </span></li>
<li><span>38      else if(function_exists('shell_exec'))  </span></li>
<li><span>39      {  </span></li>
<li>
<span>40          $</span><span>output</span><span> = </span><span>shell_exec</span><span>($command) ;  </span>
</li>
<li><span>41      }  </span></li>
<li><span>42     </span></li>
<li><span>43      else  </span></li>
<li><span>44      {  </span></li>
<li>
<span>45          $</span><span>output</span><span> = </span><span>'Command execution not possible on this system'</span><span>;  </span>
</li>
<li>
<span>46          $</span><span>return_var</span><span> = </span><span>1</span><span>;  </span>
</li>
<li><span>47      }  </span></li>
<li><span>48     </span></li>
<li>
<span>49      return array('output' =</span><span>></span><span> $output , 'status' =</span><span>></span><span> $return_var);  </span>
</li>
<li><span>50  }  </span></li>
<li><span>51     </span></li>
<li><span>52  terminal('ls'); </span></li>
</ol>

上面的函数將运行shell命令, 只要有一个系统函数可用, 这保持了代码的一致性. 

5. 灵活编写函数

<ol>
<li><span><span>1   function add_to_cart($item_id , $qty)  </span></span></li>
<li><span>2   {  </span></li>
<li><span>3       $_SESSION['cart']['item_id'] = $qty;  </span></li>
<li><span>4   }  </span></li>
<li><span>5      </span></li>
<li><span>6   add_to_cart( 'IPHONE3' , 2 ); </span></li>
</ol>

使用上面的函数添加单个项目. 而当添加项列表的时候,你要创建另一个函数吗? 不用, 只要稍加留意不同类型的参数, 就会更灵活. 如:

<ol>
<li><span><span>01  function add_to_cart($item_id , $qty)  </span></span></li>
<li><span>02  {  </span></li>
<li><span>03      if(!is_array($item_id))  </span></li>
<li><span>04      {  </span></li>
<li><span>05          $_SESSION['cart']['item_id'] = $qty;  </span></li>
<li><span>06      }  </span></li>
<li><span>07     </span></li>
<li><span>08      else  </span></li>
<li><span>09      {  </span></li>
<li>
<span>10          foreach($item_id as $</span><span>i_id</span><span> =</span><span>></span><span> $qty)  </span>
</li>
<li><span>11          {  </span></li>
<li><span>12              $_SESSION['cart']['i_id'] = $qty;  </span></li>
<li><span>13          }  </span></li>
<li><span>14      }  </span></li>
<li><span>15  }  </span></li>
<li><span>16     </span></li>
<li><span>17  add_to_cart( 'IPHONE3' , 2 );  </span></li>
<li>
<span>18  add_to_cart( array('IPHONE3' =</span><span>></span><span> 2 , 'IPAD' =</span><span>></span><span> 5) ); </span>
</li>
</ol>

现在, 同个函数可以处理不同类型的输入参数了. 可以参照上面的例子重构你的多处代码, 使其更智能.

我很想知道为什么这么多关于php建议的博客文章都没提到这点.

<ol>
<li><span><span>1   </span><span></span><span>php</span><span> </span></span></li>
<li><span>2      </span></li>
<li><span>3   echo "Hello";  </span></li>
<li><span>4      </span></li>
<li><span>5   //Now dont close this tag </span></li>
</ol>

这將节约你很多时间. 我们举个例子:

一个 super_class.php 文件

<ol>
<li><span><span>01  </span><span></span><span>php</span><span> </span></span></li>
<li><span>02  class super_class  </span></li>
<li><span>03  {  </span></li>
<li><span>04      function super_function()  </span></li>
<li><span>05      {  </span></li>
<li><span>06          //super code  </span></li>
<li><span>07      }  </span></li>
<li><span>08  }  </span></li>
<li>
<span>09  </span><span>?></span><span> </span>
</li>
<li><span>10  //super extra character after the closing tag </span></li>
</ol>

index.php

<ol>
<li><span><span>1   require_once('super_class.php');  </span></span></li>
<li><span>2      </span></li>
<li><span>3   //echo an image or pdf , or set the cookies or session data </span></li>
</ol>

这样, 你將会得到一个 Headers already send error. 为什么? 因为 “super extra character” 已经被输出了. 现在你得开始调试啦. 这会花费大量时间寻找 super extra 的位置.

因此, 养成省略关闭符的习惯：

<ol>
<li><span><span>01  </span><span></span><span>php</span><span> </span></span></li>
<li><span>02  class super_class  </span></li>
<li><span>03  {  </span></li>
<li><span>04      function super_function()  </span></li>
<li><span>05      {  </span></li>
<li><span>06          //super code  </span></li>
<li><span>07      }  </span></li>
<li><span>08  }  </span></li>
<li><span>09     </span></li>
<li><span>10  //No closing tag </span></li>
</ol>

这会更好。

7. 在某地方收集所有输入, 一次输出给浏览器这称为输出缓冲, 假如说你已在不同的函数输出内容:

<ol>
<li><span><span>01  function print_header()  </span></span></li>
<li><span>02  {  </span></li>
<li>
<span>03      echo "</span><span><span>div</span><span> </span><span>id</span><span>=</span><span>'header'</span><span>></span><span>Site Log and Login links</span><span></span><span>div</span><span>></span><span>";  </span></span>
</li>
<li><span>04  }  </span></li>
<li><span>05     </span></li>
<li><span>06  function print_footer()  </span></li>
<li><span>07  {  </span></li>
<li>
<span>08      echo "</span><span><span>div</span><span> </span><span>id</span><span>=</span><span>'footer'</span><span>></span><span>Site was made by me</span><span></span><span>div</span><span>></span><span>";  </span></span>
</li>
<li><span>09  }  </span></li>
<li><span>10     </span></li>
<li><span>11  print_header();  </span></li>
<li>
<span>12  for($</span><span>i</span><span> = </span><span>0</span><span> ; $i </span><span><span> </span><span>100</span><span>; $i++)  </span></span>
</li>
<li><span>13  {  </span></li>
<li>
<span>14      echo "I is : $i </span><span><span>br</span><span> </span><span>/></span><span>';  </span></span>
</li>
<li><span>15  }  </span></li>
<li><span>16  print_footer(); </span></li>
</ol>

替代方案, 在某地方集中收集输出. 你可以存储在函数的局部变量中, 也可以使用ob_start和ob_end_clean. 如下:

<ol>
<li><span><span>01  function print_header()  </span></span></li>
<li><span>02  {  </span></li>
<li>
<span>03      $</span><span>o</span><span> = </span><span>"<div>Site Log and Login links</div>"</span><span>;  </span>
</li>
<li><span>04      return $o;  </span></li>
<li><span>05  }  </span></li>
<li><span>06     </span></li>
<li><span>07  function print_footer()  </span></li>
<li><span>08  {  </span></li>
<li>
<span>09      $</span><span>o</span><span> = </span><span>"<div>Site was made by me</div>"</span><span>;  </span>
</li>
<li><span>10      return $o;  </span></li>
<li><span>11  }  </span></li>
<li><span>12     </span></li>
<li><span>13  echo print_header();  </span></li>
<li>
<span>14  for($</span><span>i</span><span> = </span><span>0</span><span> ; $i </span><span><span> </span><span>100</span><span>; $i++)  </span></span>
</li>
<li><span>15  {  </span></li>
<li>
<span>16      echo "I is : $i </span><span><span>br</span><span> </span><span>/></span><span>';  </span></span>
</li>
<li><span>17  }  </span></li>
<li><span>18  echo print_footer(); </span></li>
</ol>

为什么需要输出缓冲:

>>可以在发送给浏览器前更改输出. 如 str_replaces 函数或可能是 preg_replaces 或添加些监控/调试的html内容.

>>输出给浏览器的同时又做php的处理很糟糕. 你应该看到过有些站点的侧边栏或中间出现错误信息. 知道为什么会发生吗? 因为处理和输出混合了.

8. 发送正确的mime类型头信息, 如果输出非html内容的话。

输出一些xml.

<ol>
<li><span><span>1   $</span><span>xml</span><span> = </span><span>'<?xml  version="1.0" encoding="utf-8" standalone="yes"?>'</span><span>;  </span></span></li>
<li>
<span>2   $</span><span>xml</span><span> = "</span><span><span>response</span><span>></span><span> </span></span>
</li>
<li>
<span>3     </span><span><span>code</span><span>></span><span>0</span><span></span><span>code</span><span>></span><span> </span></span>
</li>
<li>
<span>4   </span><span></span><span>response</span><span>></span><span>";  </span>
</li>
<li><span>5      </span></li>
<li><span>6   //Send xml data  </span></li>
<li><span>7   echo $xml; </span></li>
</ol>

工作得不错. 但需要一些改进.

<ol>
<li><span><span>1   $</span><span>xml</span><span> = </span><span>'<?xml  version="1.0" encoding="utf-8" standalone="yes"?>'</span><span>;  </span></span></li>
<li>
<span>2   $</span><span>xml</span><span> = "</span><span><span>response</span><span>></span><span> </span></span>
</li>
<li>
<span>3     </span><span><span>code</span><span>></span><span>0</span><span></span><span>code</span><span>></span><span> </span></span>
</li>
<li>
<span>4   </span><span></span><span>response</span><span>></span><span>";  </span>
</li>
<li><span>5      </span></li>
<li><span>6   //Send xml data  </span></li>
<li><span>7   header("content-type: text/xml");  </span></li>
<li><span>8   echo $xml; </span></li>
</ol>

注意header行. 该行告知浏览器发送的是xml类型的内容. 所以浏览器能正确的处理. 很多的javascript库也依赖头信息.

类似的有 javascript , css, jpg image, png image:

JavaScript

<ol>
<li><span><span>1   header("content-type: application/x-javascript");  </span></span></li>
<li>
<span>2   echo "var </span><span>a</span><span> = </span><span>10</span><span>"; </span>
</li>
</ol>

CSS

<ol>
<li><span><span>1   header("content-type: text/css");  </span></span></li>
<li><span>2   echo "#div id { background:#000; }"; </span></li>
</ol>

9. 为mysql连接设置正确的字符编码曾经遇到过在mysql表中设置了unicode/utf-8编码, phpadmin也能正确显示, 但当你获取内容并在页面输出的时候,会出现乱码. 这里的问题出在mysql连接的字符编码.

<ol>
<li><span><span>01  //Attempt to connect to database  </span></span></li>
<li>
<span>02  $</span><span>c</span><span> = </span><span>mysqli_connect</span><span>($this-</span><span>></span><span>host , $this-</span><span>></span><span>username, $this-</span><span>></span><span>password);  </span>
</li>
<li><span>03     </span></li>
<li><span>04  //Check connection validity  </span></li>
<li><span>05  if (!$c)   </span></li>
<li><span>06  {  </span></li>
<li>
<span>07      die ("Could not connect to the database host: </span><span><span>br</span><span> </span><span>/></span><span>". mysqli_connect_error());  </span></span>
</li>
<li><span>08  }  </span></li>
<li><span>09     </span></li>
<li><span>10  //Set the character set of the connection  </span></li>
<li><span>11  if(!mysqli_set_charset ( $c , 'UTF8' ))  </span></li>
<li><span>12  {  </span></li>
<li><span>13      die('mysqli_set_charset() failed');  </span></li>
<li><span>14  } </span></li>
</ol>

一旦连接数据库, 最好设置连接的 characterset. 你的应用如果要支持多语言, 这么做是必须的.

10. 使用 htmlentities 设置正确的编码选项php5.4前, 字符的默认编码是ISO-8859-1, 不能直接输出如à a等.

<ol><li><span><span>1 $</span><span>value</span><span> = </span><span>htmlentities</span><span>($this-</span><span>></span><span>value , ENT_QUOTES , CHARSET);  </span></span></li></ol>

php5.4以后, 默认编码为UTF-8, 这將解决很多问题. 但如果你的应用是多语言的, 仍然要留意编码问题,.

11. 不要在应用中使用gzip压缩输出, 让apache处理考虑过使用 ob_gzhandler 吗? 不要那样做. 毫无意义. php只应用来编写应用. 不应操心服务器和浏览器的数据传输优化问题.

使用apache的mod_gzip/mod_deflate 模块压缩内容。

12. 使用json_encode输出动态javascript内容时常会用php输出动态javascript内容:

<ol>
<li><span><span>01  $</span><span>images</span><span> = </span><span>array</span><span>(  </span></span></li>
<li><span>02   'myself.png' , 'friends.png' , 'colleagues.png'  </span></li>
<li><span>03  );  </span></li>
<li><span>04     </span></li>
<li>
<span>05  $</span><span>js_code</span><span> = </span><span>''</span><span>;  </span>
</li>
<li><span>06     </span></li>
<li><span>07  foreach($images as $image)  </span></li>
<li><span>08  {  </span></li>
<li>
<span>09  $js_code </span><span>.</span><span>= </span><span>"'$image' ,"</span><span>;  </span>
</li>
<li><span>10  }  </span></li>
<li><span>11     </span></li>
<li>
<span>12  $</span><span>js_code</span><span> = </span><span>'var images = ['</span><span> . $js_code . ']; ';  </span>
</li>
<li><span>13     </span></li>
<li><span>14  echo $js_code;  </span></li>
<li><span>15     </span></li>
<li>
<span>16  //Output is var </span><span>images</span><span> = ['myself.png' ,'friends.png' ,'colleagues.png' ,]; </span>
</li>
</ol>

更聪明的做法, 使用 json_encode:

<ol>
<li><span><span>1   $</span><span>images</span><span> = </span><span>array</span><span>(  </span></span></li>
<li><span>2    'myself.png' , 'friends.png' , 'colleagues.png'  </span></li>
<li><span>3   );  </span></li>
<li><span>4      </span></li>
<li>
<span>5   $</span><span>js_code</span><span> = </span><span>'var images = '</span><span> . json_encode($images);  </span>
</li>
<li><span>6      </span></li>
<li><span>7   echo $js_code;  </span></li>
<li><span>8      </span></li>
<li>
<span>9   //Output is : var </span><span>images</span><span> = ["myself.png","friends.png","colleagues.png"] </span>
</li>
</ol>

优雅乎?

13. 写文件前, 检查目录写权限写或保存文件前, 确保目录是可写的, 假如不可写, 输出错误信息. 这会节约你很多调试时间. linux系统中, 需要处理权限, 目录权限不当会导致很多很多的问题, 文件也有可能无法读取等等.

确保你的应用足够智能, 输出某些重要信息.

<ol>
<li><span><span>1   $</span><span>contents</span><span> = </span><span>"All the content"</span><span>;  </span></span></li>
<li>
<span>2   $</span><span>file_path</span><span> = </span><span>"/var/www/project/content.txt"</span><span>;  </span>
</li>
<li><span>3      </span></li>
<li><span>4   file_put_contents($file_path , $contents); </span></li>
</ol>

这大体上正确. 但有些间接的问题. file_put_contents 可能会由于几个原因失败:

>>父目录不存在

>>目录存在, 但不可写

>>文件被写锁住?

所以写文件前做明确的检查更好.

<ol>
<li><span><span>01  $</span><span>contents</span><span> = </span><span>"All the content"</span><span>;  </span></span></li>
<li>
<span>02  $</span><span>dir</span><span> = </span><span>'/var/www/project'</span><span>;  </span>
</li>
<li>
<span>03  $</span><span>file_path</span><span> = $dir . "/content.txt";  </span>
</li>
<li><span>04     </span></li>
<li><span>05  if(is_writable($dir))  </span></li>
<li><span>06  {  </span></li>
<li><span>07      file_put_contents($file_path , $contents);  </span></li>
<li><span>08  }  </span></li>
<li><span>09  else  </span></li>
<li><span>10  {  </span></li>
<li><span>11      die("Directory $dir is not writable, or does not exist. Please check");  </span></li>
<li><span>12  } </span></li>
</ol>

这么做后, 你会得到一个文件在何处写及为什么失败的明确信息.

14. 更改应用创建的文件权限在 linux环境中, 权限问题可能会浪费你很多时间. 从今往后, 无论何时, 当你创建一些文件后, 确保使用chmod设置正确权限. 否则的话, 可能文件先是由"php"用户创建, 但你用其它的用户登录工作, 系统將会拒绝访问或打开文件, 你不得不奋力获取root权限, 更改文件的权限等等.

<ol>
<li><span><span>1   // Read and write for owner, read for everybody else  </span></span></li>
<li><span>2   chmod("/somedir/somefile", 0644);  </span></li>
<li><span>3      </span></li>
<li><span>4   // Everything for owner, read and execute for others  </span></li>
<li><span>5   chmod("/somedir/somefile", 0755); </span></li>
</ol>

15. 不要依赖submit按钮值来检查表单提交行为

<ol>
<li><span><span>1   if($_POST['submit'] == 'Save')  </span></span></li>
<li><span>2   {  </span></li>
<li><span>3       //Save the things  </span></li>
<li><span>4   } </span></li>
</ol>

上面大多数情况正确, 除了应用是多语言的. 'Save' 可能代表其它含义. 你怎么区分它们呢. 因此, 不要依赖于submit按钮的值.

<ol>
<li><span><span>1   if( $_SERVER['REQUEST_METHOD'] == 'POST' and isset($_POST['submit']) )  </span></span></li>
<li><span>2   {  </span></li>
<li><span>3       //Save the things  </span></li>
<li><span>4   } </span></li>
</ol>

现在你从submit按钮值中解脱出来了.

16. 为函数内总具有相同值的变量定义成静态变量

<ol>
<li><span><span>1   //Delay for some time  </span></span></li>
<li><span>2   function delay()  </span></li>
<li><span>3   {  </span></li>
<li>
<span>4       $</span><span>sync_delay</span><span> = </span><span>get_option</span><span>('sync_delay');  </span>
</li>
<li><span>5      </span></li>
<li>
<span>6       echo "</span><span><span>br</span><span> </span><span>/></span><span>Delaying for $sync_delay seconds...";  </span></span>
</li>
<li><span>7       sleep($sync_delay);  </span></li>
<li>
<span>8       echo "Done </span><span><span>br</span><span> </span><span>/></span><span>";  </span></span>
</li>
<li><span>9   } </span></li>
</ol>

17. 不要直接使用 $_SESSION 变量

某些简单例子:

<ol>
<li><span><span>1 $_SESSION['username'] = $username;  </span></span></li>
<li><span> </span></li>
<li>
<span>2 $</span><span>username</span><span> = $_SESSION['username'];  </span>
</li>
<li><span> </span></li>
</ol>

这会导致某些问题. 如果在同个域名中运行了多个应用, session 变量可能会冲突. 两个不同的应用可能使用同一个session key. 例如, 一个前端门户, 和一个后台管理系统使用同一域名.

从现在开始, 使用应用相关的key和一个包装函数:

<ol>
<li><span><span>01  define('APP_ID' , 'abc_corp_ecommerce');  </span></span></li>
<li><span>02     </span></li>
<li><span>03  //Function to get a session variable  </span></li>
<li><span>04  function session_get($key)  </span></li>
<li><span>05  {  </span></li>
<li>
<span>06      $</span><span>k</span><span> = </span><span>APP_ID</span><span> . '.' . $key;  </span>
</li>
<li><span>07     </span></li>
<li><span>08      if(isset($_SESSION[$k]))  </span></li>
<li><span>09      {  </span></li>
<li><span>10          return $_SESSION[$k];  </span></li>
<li><span>11      }  </span></li>
<li><span>12     </span></li>
<li><span>13      return false;  </span></li>
<li><span>14  }  </span></li>
<li><span>15     </span></li>
<li><span>16  //Function set the session variable  </span></li>
<li><span>17  function session_set($key , $value)  </span></li>
<li><span>18  {  </span></li>
<li>
<span>19      $</span><span>k</span><span> = </span><span>APP_ID</span><span> . '.' . $key;  </span>
</li>
<li><span>20      $_SESSION[$k] = $value;  </span></li>
<li><span>21     </span></li>
<li><span>22      return true;  </span></li>
<li><span>23  } </span></li>
</ol>

18. 將工具函数封装到类中

假如你在某文件中定义了很多工具函数:

<ol>
<li><span><span>01  function utility_a()  </span></span></li>
<li><span>02  {  </span></li>
<li><span>03      //This function does a utility thing like string processing  </span></li>
<li><span>04  }  </span></li>
<li><span>05     </span></li>
<li><span>06  function utility_b()  </span></li>
<li><span>07  {  </span></li>
<li><span>08      //This function does nother utility thing like database processing  </span></li>
<li><span>09  }  </span></li>
<li><span>10     </span></li>
<li><span>11  function utility_c()  </span></li>
<li><span>12  {  </span></li>
<li><span>13      //This function is ...  </span></li>
<li><span>14  } </span></li>
</ol>

这些函数的使用分散到应用各处. 你可能想將他们封装到某个类中:

<ol>
<li><span><span>01  class Utility  </span></span></li>
<li><span>02  {  </span></li>
<li><span>03      public static function utility_a()  </span></li>
<li><span>04      {  </span></li>
<li><span>05     </span></li>
<li><span>06      }  </span></li>
<li><span>07     </span></li>
<li><span>08      public static function utility_b()  </span></li>
<li><span>09      {  </span></li>
<li><span>10     </span></li>
<li><span>11      }  </span></li>
<li><span>12     </span></li>
<li><span>13      public static function utility_c()  </span></li>
<li><span>14      {  </span></li>
<li><span>15     </span></li>
<li><span>16      }  </span></li>
<li><span>17  }  </span></li>
<li><span>18     </span></li>
<li><span>19  //and call them as  </span></li>
<li><span>20     </span></li>
<li>
<span>21  $</span><span>a</span><span> = </span><span>Utility</span><span>::utility_a();  </span>
</li>
<li>
<span>22  $</span><span>b</span><span> = </span><span>Utility</span><span>::utility_b(); </span>
</li>
</ol>

显而易见的好处是, 如果php内建有同名的函数, 这样可以避免冲突.

另一种看法是, 你可以在同个应用中为同个类维护多个版本, 而不导致冲突. 这是封装的基本好处，无它。