Mine

<?php
class validate_Form {
	
  public $_define_string;
  
  public function __empty($_define_string) {
	  if(empty($_define_string)) {
		return 0;  
	  } else {
		  return 1;
	  }
  }
  
  public function __mail($_define_string) {
	 if (!preg_match("/^[0-9a-zA-Z-_.]+@[0-9a-zA-Z-.]+\.[0-9a-zA-Z.]+$/", $_define_string)) {
		return 0;	 
	  } else {
		  return 1;
	  }
  }
  
  
}

$variable = new validate_form();

$test_post = 'me@php.net';
if(!$variable->__mail($test_post)){
	echo 'E-mail is not valid';
}

$test_post = 'mephp.net';
if(!$variable->__mail($test_post)){
	echo 'E-mail is not valid';
}
?>