首先我们来看php官方手册中对include的文件搜索原则的描述:
Files for including are first looked for in each include_path entry relative to the current working directory, and then in the directory of current script. E.g. if your include_path is libraries , current working directory is , you included and there is include "b.php" in that file, is first looked in and then in . If filename begins with ./ or ../ , it is looked only in the current working directory.
寻找包含文件的顺序先是在当前工作目录的相对的 include_path 下寻找,然后是当前运行脚本所在目录相对的 include_path 下寻找。例如 include_path 是 . ,当前工作目录是 ,脚本中要 include 一个 并且在该文件中有一句 include "b.php" ,则寻找 的顺序先是 ,然后是 。如果文件名以 ./ 或者 ../ 开始,则只在当前工作目录相对的 include_path 下寻找。
所以如下所示的文件结构
—-a.php
—-i@本文来源gaodai$ma#com搞$代*码6网搞代gaodaima码nclude/b.php
—-include/c.php
其中a.php
<?phpinclude 'include/b.php';?>-----------------------b.php<?phpinclude 'c.php';include 'include/c.php';?>
————————–
c.php
<?phpecho 'c.php';?>
————————–
都能正确运行,说明b.php中两种不同包含路径都是可行的,根据include寻找包含文件的方式都能找到c.php。
但是最好的方式还是使用绝对路径,如果使用了绝对路径,php内核就直接通过路径去载入文件而不用去include path逐个搜索文件,增加了代码执行效率
<?phpdefine('ROOT_PATH',dirname(FILE));include ROOT_PATH.'/c.php';?>
不同的文件包含方式,程序的执行性能比较具体可以参照此文
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