Why does this PHP relative include fail?

disc@puff:~/php$ ls 
a.php  data  include 

disc@puff:~/php$ tree 
. 
├── a.php 
├── data 
│   └── d.php 
└── include 
    ├── b.php 
    └── c.php 
2 directories, 4 files 

disc@puff:~/php$ cat a.php 
a.php is including include/b.php ... 
<?php include "include/b.php" ?> 

disc@puff:~/php$ cat include/b.php 
b.php is including c.php and ../data/d.php ... 
<?php include "c.php" ?> 
<?php include "../data/d.php" ?> 

disc@puff:~/php$ cat include/c.php 
c.php 

disc@puff:~/php$ cat data/d.php 
d.php 

disc@puff:~/php$ php a.php 
a.php is including include/b.php ... 
b.php is including c.php and ../data/d.php ... 
c.php 
PHP Warning:  include(../data/d.php): failed to open stream: No 
such file or directory in /home/disc/php/include/b.php on line 3 
PHP Warning:  include(): Failed opening '../data/d.php' for 
inclusion (include_path='.:/usr/share/php:/usr/share/pear') in /home/ 
disc/php/include/b.php on line 3 

disc@puff:~/php$

Why does include "c.php" succeed but include "../data/d.php" fail?

http://www.php.net/manual/en/function.include.php mentions: "If a path is defined — whether absolute (starting with a drive letter or \ on Windows, or / on Unix/Linux systems) or relative to the current directory (starting with . or ..) — the include_path will be ignored altogether. For example, if a filename begins with ../, the parser will look in the parent directory to find the requested file. "

Parent directory of what?

回答1:

paths are always relative to the script which got called. in your example c.php is loaded because "." (current directory) is always in the include_path.

to fix this you can use dirname(__FILE__) to always know the directory of the file itself. (the file in which you write FILE)

or you can use dirname($_SERVER['SCRIPT_FILENAME']) to alwys get the directory of the caling script.

回答2:

As you're starting with a.php, you should define the include directories in a.php:

define('MY_INCLUDES', dirname(__FILE__) . '/include/');
define('MY_DATA', dirname(__FILE__) . '/data/');

Afterwards include the files with absolute paths:

include(MY_INCLUDES . 'b.php');
include(MY_DATA . 'c.php');