Execution time limit exceeded with PHP random number generator

I'm trying to make a program that prints a random number every 3 seconds, but my mistake is "Maximum execution time of 30 seconds exceeded", sorry but I have almost no experience in PHP and I know the functions to clear the memory, I appreciate your help .

ejemplo();
function ejemplo() {
    $c=null; 
    $c=mt_rand(60,200); 
    sleep(3); 
    clear();
    ejemplo(); 
}