mysqli_real_escape_string() expects exactly 2 parameters in mysqli

PHP
2

Well, the error message says

mysqli_real_escape_string() expects exactly 2 parameters, 1 given

The example code has

mysqli_real_escape_string((int)$id);
mysqli_real_escape_string((int)$_GET['add']);

int in parentheses is not a parameter

http://php.net/manual/en/mysqli.real-escape-string.php