PHP is_dir Function
PHP is_dir function tutorial shows how to check if a path is a directory in PHP. Learn is_dir with practical examples.
PHP is_dir Function
last modified April 3, 2025
The PHP is_dir function checks whether a path is a directory. It’s essential for filesystem operations where directory validation is needed.
Basic Definition
The is_dir function checks if the given filename is a directory. It returns true if the filename exists and is a directory, false otherwise.
Syntax: is_dir(string $filename): bool. The function caches results, so multiple calls may return cached values until clearstatcache() is called.
Basic is_dir Example
This shows the simplest usage of is_dir to check a directory.
basic_is_dir.php
<?php
declare(strict_types=1);
$path = “/var/www/html”; $isDirectory = is_dir($path);
var_dump($isDirectory); // Outputs: bool(true) if directory exists
This checks if “/var/www/html” is a directory. The function returns true only if the path exists and is a directory, not a file or symlink.
Checking Relative Paths
is_dir works with relative paths from the current working directory.
relative_path.php
<?php
declare(strict_types=1);
$path = “docs”; $isDirectory = is_dir($path);
echo $isDirectory ? “Directory exists” : “Not a directory”;
This checks if “docs” is a directory relative to the current script location. Remember that relative paths depend on the current working directory.
Checking Non-Existent Path
is_dir returns false for paths that don’t exist or aren’t directories.
nonexistent_path.php
<?php
declare(strict_types=1);
$path = “/nonexistent/path”; $isDirectory = is_dir($path);
var_dump($isDirectory); // Outputs: bool(false)
The function returns false for non-existent paths. It doesn’t throw errors for invalid paths, making it safe for existence checking.
Checking File vs Directory
This example demonstrates differentiating between files and directories.
file_vs_dir.php
<?php
declare(strict_types=1);
$path1 = “/var/www/html/index.php”; $path2 = “/var/www/html”;
$result1 = is_dir($path1) ? “Directory” : “Not directory”; $result2 = is_dir($path2) ? “Directory” : “Not directory”;
echo $result1 . “\n”; // Outputs: Not directory echo $result2 . “\n”; // Outputs: Directory
This shows how is_dir correctly identifies files vs directories. It’s useful for filesystem traversal where you need to handle each differently.
Windows Path Example
is_dir works with Windows-style paths using backslashes.
windows_path.php
<?php
declare(strict_types=1);
$path = “C:\Windows\System32”; $isDirectory = is_dir($path);
echo $isDirectory ? “Valid Windows directory” : “Invalid directory”;
The function handles Windows paths correctly. Note that backslashes need to be escaped in PHP strings, or you can use forward slashes which also work.
Best Practices
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Permission Checks: Verify read permissions before checking.
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Error Handling: Combine with file_exists for robust checks.
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Symbolic Links: Use is_link with is_dir for symlink handling.
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Performance: Cache results when checking repeatedly.
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Security: Sanitize paths before filesystem operations.
Source
This tutorial covered the PHP is_dir function with practical examples showing directory validation in different scenarios.
Author
My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.
