Description:
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http://docs.php.net/manual/en/install.unix.apache2.php

Tell Apache to parse certain extensions as PHP. For example, let's have Apache parse .php files as PHP. Instead of only using the Apache AddType directive, we want to avoid potentially dangerous uploads and created files such as exploit.php.jpg from being executed as PHP. Using this example, you could have any extension(s) parse as PHP by simply adding them. We'll add .php to demonstrate. 

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http://docs.php.net/manual/zh/install.unix.apache2.php

In chinese version，is not update.It is a security problem.

15. 告知 Apache 将特定的扩展名解析成 PHP，例如，让 Apache 将扩展名 .php
    解析成 PHP。可以将任何扩展名指定为 PHP，只需添加它们，每一个用空格分隔。
    例如，要添加 .phtml：
    AddType application/x-httpd-php .php .phtml
    通常还将 .phps 扩展名设置成显示高亮的 PHP 源文件，可以这样来完成：
    AddType application/x-httpd-php-source .phps