Determine the Parent Directory of a Path in PHP

Written by Cory S.N. LaViska on June 18th, 2008

A PHP function that returns the parent directory of the specified path.

Examples

Input	Returns
`/var/www/htdocs/images/`	`/var/www/htdocs/`
`/var/www/htdocs/images`	`/var/www/htdocs/`
`/var/www/htdocs/index.php`	`/var/www/htdocs/`
`c:\www\files\folder\`	`c:\www\files\`

Notes

If a single backslash is detected, all slashes are assumed to be backslashes (as on a Windows file system)
Trailing slash is not required, but will always be returned
If $convert_backslashes is true, backslashes will be converted to forward slashes

<?php

function parent_directory($path, $convert_backslashes = false) {

    // Detect backslashes

    if( strstr($path, '\\') ) $backslash = true;

    // Convert backslashes to forward slashes

    $path = str_replace('\\', '/', $path);

    // Add trailing slash if non-existent

    if( substr($path, strlen($path) - 1) != '/' ) $path .= '/';

    // Determine parent path

    $path = substr($path, 0, strlen($path) - 1);

    $path = substr( $path, 0, strrpos($path, '/') ) . '/';

    // Convert backslashes back

    if( !$convert_backslashes && $backslash ) $path = str_replace('/', '\\', $path);

    return $path;

}

?>

Comments

Why don't you simply use PHP's inbuilt dirname() function?

#1 Jatinder on Jul 6th, 2008

@Jatinder: dirname() doesn't return the parent directory. From the PHP Manual, "Given a string containing a path to a file, this function will return the name of the directory."

#2 Cory S.N. LaViska on Jul 7th, 2008

@Cory It returns the path of the directory. You can nest calls to it, so dirname(dirname($filepath)) will return the full path of the parent directory.

I use this a lot for relative paths to the current file - i.e. dirname(dirname(__FILE__))

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