<?php

$number = "a421zx";
$number1 = "asfqe";

$matches = array();

$regexp = '/^[a-z](0-9){3}[a-z]{2}$/';

if (preg_match($regexp, $number, $matches)) {
	    echo "All right";
	    var_dump($matches);
	    
} else {
	echo "Uncorrectly. Please, kill yorself\n";
}


if (preg_match($regexp, $number1, $matches)) {
	    echo "All right";
	    var_dump($matches);
	    
} else {
	echo "Uncorrectly. Please, kill yorself\n";
}