PHP Include Paths: Relative to the File or the Calling Script?

Understanding PHP Relative Include Paths

When using PHP include paths, it can be confusing to determine the reference point for relative paths. This article clarifies the behavior of include paths in PHP and answers the question: Are include paths relative to the file or the calling code?

Relative Path Reference

In PHP, include paths are always relative to the main script executing the include statement. This means that the location of the file containing the include will determine the base reference for the relative path.

Example:

Consider the following scenario:

• A.php includes B.php
• B.php includes C.php

In this case, the relative path to C.php is relative to the location of A.php, not B.php.

Implication:

The file from which the include is called is irrelevant. The only thing that matters is the location of the main script.

Current Working Directory

The current working directory does not affect the reference point of relative paths. The base directory is always determined by the location of the main script.

Using FILE or DIR

If you wish to make the include path relative to the file containing the include, you can use the FILE or DIR constants. These constants provide the absolute path to the current file.

Example:

include(dirname(__FILE__)."/C.PHP");

This syntax would include the file "C.php" relative to the directory of the file containing the include statement.

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