Master PHP fileperms(): Retrieve and Decode File Permissions Easily

Summary

In PHP development you can obtain a file's permission bits using the built-in fileperms() function. The function accepts a file path string and returns an integer where the low 9 bits represent read, write and execute permissions for owner, group and others.

A simple example:

<?php
$filename = 'test.txt';
$perms = fileperms($filename);
echo "File {$filename} permissions: {$perms}";
?>

The returned integer can be converted to the familiar symbolic string (e.g. -rw-r--r--) by applying bitwise masks. The article provides a helper format_perms() function that checks the various bits (0xC000, 0xA000, etc.) and builds the permission string.

<?php
function format_perms($perms) {
    $result = '';
    if (($perms & 0xC000) == 0xC000) { $result .= 's'; }
    elseif (($perms & 0xA000) == 0xA000) { $result .= 'l'; }
    elseif (($perms & 0x8000) == 0x8000) { $result .= '-'; }
    elseif (($perms & 0x6000) == 0x6000) { $result .= 'b'; }
    elseif (($perms & 0x4000) == 0x4000) { $result .= 'd'; }
    elseif (($perms & 0x2000) == 0x2000) { $result .= 'c'; }
    elseif (($perms & 0x1000) == 0x1000) { $result .= 'p'; }
    else { $result .= 'u'; }

    $result .= ($perms & 0x0100) ? 'r' : '-';
    $result .= ($perms & 0x0080) ? 'w' : '-';
    if ($perms & 0x0040) {
        $result .= ($perms & 0x0800) ? 's' : 'x';
    } else {
        $result .= ($perms & 0x0800) ? 'S' : '-';
    }
    $result .= ($perms & 0x0020) ? 'r' : '-';
    $result .= ($perms & 0x0010) ? 'w' : '-';
    if ($perms & 0x0008) {
        $result .= ($perms & 0x0400) ? 't' : 'x';
    } else {
        $result .= ($perms & 0x0400) ? 'T' : '-';
    }
    $result .= ($perms & 0x0004) ? 'r' : '-';
    $result .= ($perms & 0x0002) ? 'w' : '-';
    $result .= ($perms & 0x0001) ? 'x' : '-';
    return $result;
}
$filename = 'test.txt';
$perms = fileperms($filename);
$formatted_perms = format_perms($perms);
echo "File {$filename} permissions: {$formatted_perms}";
?>

Running the script prints something like File test.txt permissions: -rw-r--r--, demonstrating how to read and format file permissions in PHP.