$text = ' email@domain.com ';
 
function parseTextForEmail($text) {
	$email = array();
	$invalid_email = array();
 
	$text = ereg_replace("[^A-Za-z._0-9@ ]"," ",$text);
 
	$token = trim(strtok($text, " "));
 
	while($token !== "") {
 
		if(strpos($token, "@") !== false) {		
 
			$token = ereg_replace("[^A-Za-z._0-9@]","", $token);
 
			//checking to see if this is a valid email address
			if(is_valid_email($email) !== true) {
				$email[] = strtolower($token);
			}
			else {
				$invalid_email[] = strtolower($token);
			}
		}
 
		$token = trim(strtok(" "));
	}
 
	$email = array_unique($email);
	$invalid_email = array_unique($invalid_email);
 
	return array("valid_email"=>$email, "invalid_email" => $invalid_email);
 
}
 
function is_valid_email($email) {
	if (eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.([a-z]){2,4})$",$email)) return true;
	else return false;
}
 
var_dump(parseTextForEmail($text));