php validate integer

Can use

$validatedValue = filter_input(INPUT_GET, 'id', FILTER_VALIDATE_INT);

See http://php.net/filter_input and related functions.

The manual says:

To test if a variable is a number or a numeric string (such as form input, which is always a string), you must use is_numeric().

Alternative you can use the regex based test as:

if(preg_match('/^\d+$/',$_GET['id'])) {
  // valid input.
} else {
  // invalid input.
}

What about intval?

$int = intval($_GET['id']);

To validate form data (string) as an integer, you should use ctype_digit() It returns TRUE if every character in the string text is a decimal digit, FALSE otherwise. (PHP 4 >= 4.0.4, PHP 5)

Reference: http://php.net/manual/en/function.ctype-digit.php