if($_POST['enviar'] and preg_match('/^[0-9a-zA-Z]*[@]*[gmail | yahoo | hotmail]*[.]*[com]/' ,$_POST['correo'] ) ){
echo "<span class='validacion'></br>Introduzca el
[email protected]</span>";
}
else if($_POST['enviar'] and preg_match('/^[0-9a-zA-Z][.-_][0-9a-zA-Z]*[@]*[gmail | yahoo | hotmail]*[.]*[com]/' ,$_POST['correo'] ) ){
echo "<span class='validacion'></br>Introduzca el
[email protected]</span>";
}