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Explanation of usage of php DIRECTORY_SEPARATOR constant

Jul 14, 2017 am 11:14 AM
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DIRECTORY_SEPARATOR是一个显示系统分隔符的命令,是PHP中的一个预定义常量。下面本篇文章给大家介绍一下该常量的使用方法,希望对大家有帮助。

Explanation of usage of php DIRECTORY_SEPARATOR constant

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DIRECTORY_SEPARATOR是一个显示系统分隔符的命令,DIRECTORY_SEPARATOR是PHP的内部常量,不需要任何定义与包含即可直接使用。

众所周知,在windows下路径分隔符是(当然/在部分系统上也是可以正常运行的),在linux上路径的分隔符是/,这就导致了一个问题;

比如开发机器是windows,有一个图片上传程序,调试机器上指定的上传文件保存目录是:

define(‘ROOT’, dirname(FILE).”upload”)
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在本地调试都很正常,但是上传到linux服务器的时候会发现会出错。

这个问题就是出在文件的分隔符上,windows上习惯性的使用作为文件分隔符,但是在linux上人家是不认识这个标识的,人家只认识/,于是就要引入下面这个php内置变量了:DIRECTORY_SEPARATOR

上面的写法可以改写为以下无错写法:

define(‘ROOT’, dirname(FILE).DIRECTORY_SEPARATOR.”upload”);
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这样就可以确保不会出错了。

例如discuz里面是这样写的:

define(‘S_ROOT’, dirname(FILE).DIRECTORY_SEPARATOR);
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回到问题本身上,DIRECTORY_SEPARATOR是一个返回跟操作系统相关的路径分隔符的php内置命令,在windows上返回,而在linux或者类unix上返回/,就是这么个区别,通常在定义包含文件路径或者上传保存目录的时候会用到。

require_once dirname(FILE).DIRECTORY_SEPARATOR . './../../../wp-config.php';
require_once dirname(FILE).DIRECTORY_SEPARATOR.'inc/options.php';
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这两句PHP代码,为什么前面部分用DIRECTORY_SEPARATOR,而后面部分却用"/"呢?

众所周知,windows下的是\和/,而LINUX下的是/

在程序本地运行很正常,上传到服务器后,发现图片没有显示出来,图片链接是绝对路径 var/,而且当中带有 \ 但是我记得这个路径已经处理成相对路径的

$path    = dirname(dirname(dirname(FILE))).'\\';
$search = array( $path, '\\');
$replace = array( '', '/');
return str_replace($search,$replace,$this->tempfolder).$this->filename_prefix.$public.'.jpg';
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第一行代码的用在LINUX "\\", 就不行。

解决的办法是 :

用PHP 预定义常量DIRECTORY_SEPARATOR来代替'\','/'这样的路径分隔符,以前觉得既然windows,LINUX 都支持/,那都用成 / 得了,这是没错的。

可是从这个例子可以看出,当要对路径字符串进行处理的时候,就比较危险了,所以最好还是用DIRECTORY_SEPARATOR吧!

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