mysql - Where can I find documentation for PHP's escape_data() function? -

i need validate submitted form using php. i'm noob , working off of example uses escape_data() instead of mysql_real_escape_string(). can find thorough explanation escape_data() (there's nothing in php documentation)?

here's example code:

if (empty($_post['email'])) {     $errors[] = 'you forgot enter email address.'; } else {     $e = escape_data($_post['email']); } 

there no such function escape_data in php. must user defined function. please refer source copied it.