PHP 的 _FILE_ 恒量
PHP 的 __FILE__ 常量
今天碰到了PHP的常量__FILE__的问题了。
在网上查了一下。总结了以下规律。
dirname(__FILE___) 函数返回的是脚本所在在的路径。
比如文件 b.php 包含如下内容:
<span style="color: #008080;">1</span> <span style="color: #000000;">php </span><span style="color: #008080;">2</span> <span style="color: #800080;">$basedir</span> = <span style="color: #008080;">dirname</span>(<span style="color: #ff00ff;">__FILE__</span><span style="color: #000000;">); </span><span style="color: #008080;">3</span> ?>
如果b.php被其他目录里的a.php文件require 或者 include 去引用的话。
变量$basedir 的内容还是b.php所在的那个文件夹的路径。
而不是变成a.php文件所在的目录。
dirname(__FILE__) 一般会返回文件所的当前目录到系统根目录的一个目录结构。
不会返回当前的文件名称。
dirname(__FILE__) 也可能返回一个 . (当前目录)
[原因是 b.php 文件在 http.conf 或者 PHP 配置开发环境的默认WEB目录下.
比如 WEB_ROOT 为: "C:/root/www/".]
b.php文件路径为: "C:/root/www/b.php".
使用方法提示,
如果重复一次可以把目录往上提升一个层次:
比如:$d = dirname(dirname(__FILE__));
其实就是把一个目录给dirname()做参数了.因为dirname()返回最后的目录不带\\或者是/
所以重复使用的时候可以认为 dirname() 把最下层的目录当成文件名来处理了.照常返回当前目录的上级目录.
这样重复就得到了它的上一级的目录.
包含得到上一级目录的文件
include(dirname(__FILE__).'/../filename.php');

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