Ver original<?php$string = 'foobarbaz';if(preg_match('/^[A-Za-z0-9_]+$/', $string)){ echo 'Es correcto';}else{ echo 'Es incorrecto';} $string = 'foobárbaz';if(preg_match('/^[A-Za-z0-9_]+$/', $string)){ echo 'Es correcto';}else{ echo 'Es incorrecto';}