syntax: 

  IF (condition) {

     // do something !!!

  } elseIF (condition) {

     // do something else !!!

  } else {

     // do last result

  }

  switch ($gender) {

   case 'm':

     echo 'Male ';

     break;

   case 'f':

     echo 'Female ';

     break;

   default :

     echo 'You forgot to enter your gender ? ';

     break;

  }

Logical Operator

Other Common Testing Functions

String Slashing

     $comments = stripslashes( $comments );

Numerics 

     If ( is_numeric($post))

        returns a TRUE, If $post is a number or contains any valid numbers

Empty String 

    IF (empty ($_POST['name']))

       returns a TRUE, If $_POST['name'] is empty or contains nothing or NO value at all, but NOT NULL

String size 

    IF (strlen ( $_POST['name']) > 0)

       returns a TRUE, If $_POST['name'] is not NULL or not Empty at all or contains a value either numberic or string or both

Control Vales 

    use isset to test, IF a control value had been set or even for testing Cookies

    ex.: If (isset($_POST['submit'])) .....