This function and decoct work great when working with file permissions. For example:
<?php
$mode = octdec('4750');
$user['suid'] = ($mode & 04000);
$user['read'] = ($mode & 00400);
$user['write'] = ($mode & 00200);
$user['execute'] = ($mode & 00100);
$group['sgid'] = ($mode & 02000);
$group['read'] = ($mode & 00040);
$group['write'] = ($mode & 00020);
$group['execute'] = ($mode & 00010);
$other['text'] = ($mode & 01000);
$other['read'] = ($mode & 00004);
$other['write'] = ($mode & 00002);
$other['execute'] = ($mode & 00001);
$attrs = array('-','-','-','-','-','-','-','-','-','-');
if ($system['dir']) $attrs[0] = 'd';
if ($user['read']) $attrs[1] = 'r';
if ($user['write']) $attrs[2] = 'w';
if ($user['execute']) $attrs[3] = 'x';
if ($user['suid']) $attrs[3] = 'S';
if ($group['read']) $attrs[4] = 'r';
if ($group['write']) $attrs[5] = 'w';
if ($group['execute']) $attrs[6] = 'x';
if ($group['sgid']) $attrs[6] = 'S';
if ($other['read']) $attrs[7] = 'r';
if ($other['write']) $attrs[8] = 'w';
if ($other['execute']) $attrs[9] = 'x';
if ($other['text']) $attrs[9] = 'T';
echo '<pre>';
echo 'Mode Decimal: ' . $mode . "\n";
echo 'Mode Octal: ' . decoct($mode) . "\n";
echo 'Mode String: ' . implode('',$attrs)."\n";
echo '</pre>';
?>
Outputs:
Mode Decimal: 2536
Mode Octal: 4750
Mode String: -rwSr-x---
-Mike