php randomly displays image code

PHP generates random numbers through the rand() function. This function can generate a number within a specified range.
This code randomly selects pictures through the generated random numbers

 srand( microtime() * 1000000 );
 $num = rand( 1, 4 );

 switch( $num )
 {
 case 1: $image_file = "/home/images/alfa.jpg";
 break;
 case 2: $image_file = "/home/images/ferrari.jpg";
 break;
 case 3: $image_file = "/home/images/jaguar.jpg";
 break;
 case 4: $image_file = "/home/images/porsche.jpg";
 break;
 }
 echo " Random Image : ";
?>

php