PHP Manual: is

Description

function is_writable(string $filename): bool

Returns true if the filename exists and is writable. The filename argument may be a directory name allowing you to check if a directory is writable.

Keep in mind that PHP may be accessing the file as the user id that the web server runs as (often 'nobody').

Parameters

filename: The filename being checked.

Return Values

Returns true if the filename exists and is writable.

Errors/Exceptions

Upon failure, an E_WARNING is emitted.

Examples

Example #1 is_writable() example

<?php
$filename = 'test.txt';
if (is_writable($filename)) {
    echo 'The file is writable';
} else {
    echo 'The file is not writable';
}
?>

Notes

Note:
For local files, the result of this function is not cached and the file is checked again on every call. For paths using other wrappers the result is cached. See clearstatcache() for more details.

Tip

As of PHP 5.0.0, this function can also be used with some URL wrappers. Refer to Supported Protocols and Wrappers to determine which wrappers support stat() family of functionality.