<?php
function matchIndetifier($str) {
if ($str != preg_replace("/[^0-9a-z]/i", "", $str)) {
//Invalid contains characters other than a-zA-Z0-9.
}
if (isnumeric($str)) {
//999999
}
if ($str != preg_replace("/\d/", "", $str)) {
//At this part, it's not numeric, but still has numbers. Invalid.
}
if (ucfirst($str) == $str) {
//Ullllll
}
if (strtolower($str) == $str) {
//llllll
}
if (strtoupper($str) == $str) {
//UUUUUU
}
}