How to Use PHP’s is_writable() to Check File and Directory Permissions

Syntax of is_writable()

bool is_writable ( string $filename )

The $filename parameter specifies the path of the file or directory to be examined.

Using is_writable()

Check if a file is writable

The function returns true when the file exists and is writable; otherwise it returns false. Example:

$filename = 'example.txt';
if (is_writable($filename)) {
    echo 'File is writable';
} else {
    echo 'File is not writable';
}

This code defines $filename with the target file path, calls is_writable(), and outputs the result based on the return value.

Check if a directory is writable

The same function can test directory write permissions. Example:

$directory = 'example';
if (is_writable($directory)) {
    echo 'Directory is writable';
} else {
    echo 'Directory is not writable';
}

Here $directory holds the directory path, and is_writable() determines its writeability.

Check file existence before testing writability

Combine file_exists() with is_writable() to handle missing files:

$filename = 'example.txt';
if (file_exists($filename)) {
    if (is_writable($filename)) {
        echo 'File exists and is writable';
    } else {
        echo 'File exists but is not writable';
    }
} else {
    echo 'File does not exist';
}

This script first verifies the file's existence, then checks its write permission.

Check write permission of a file or directory

Use is_writable() directly to test whether a path has write permission, regardless of it being a file or a directory:

$filename = 'example.txt';
if (is_writable($filename)) {
    echo 'File or directory has write permission';
} else {
    echo 'File or directory does not have write permission';
}

The function returns true if the specified path is writable, otherwise false.

Summary

The is_writable() function is a simple yet powerful tool for determining whether a file or directory can be written to; by passing the target path, developers can quickly assess write permissions and handle files accordingly.