<?php

function myRandomChars($theLength = 64) {
    $myChars = 'ABCDEFGHLMNOPKRSTUVWXYZ1234567890-*/$^!:;,<>';
    $myId = '';
    $length = strlen($myChars);
    for($i=0; $i<=$theLength; $i++) {
        $myId .= $myChars[rand(0, $length - 1)];
    }
    return $myId;
}

echo myRandomChars();
echo '<br><font face="Tahoma" color="red">' .strlen(myRandomChars()). '</font>';