How to Retrieve and Interpret File Permissions in PHP with fileperms()

In PHP development you often need to know whether a file is readable, writable or executable. The built‑in fileperms() function returns the permission bits of a given file path as an integer.

Function prototype

string fileperms ( string $filename )

The $filename argument is the path to the file whose permissions you want to query. The function returns an integer that encodes the file mode.

Simple usage example

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

Running this script might output something like 33204. The integer represents the permission bits; the lower nine bits correspond to the classic Unix read/write/execute flags for owner, group, and others.

Understanding the bits

Bit 0 (0x0001) – execute for others

Bit 1 (0x0002) – write for others

Bit 2 (0x0004) – read for others

Bit 3 (0x0008) – execute for group (with set‑gid handling)

Bit 4 (0x0010) – write for group

Bit 5 (0x0020) – read for group

Bit 6 (0x0040) – execute for owner (with set‑uid handling)

Bit 7 (0x0080) – write for owner

Bit 8 (0x0100) – read for owner

Because the integer mixes file type and permission bits, you typically need to mask and shift the value to extract a readable string.

Helper function to format permissions

<?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;
}
?>

This function examines the mode bits and builds a string similar to the output of ls -l, e.g., -rw-r--r--.

Full example with formatted output

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

When executed, the script might display File test.txt permissions: -rw-r--r--, showing that the owner can read and write, while the group and others can only read.

Conclusion

Using fileperms() together with a small formatter lets PHP developers quickly inspect file permission settings, ensuring that file operations respect the intended access controls.