how to use setinterval function in php code example

Example 1: setinterval php

setInterval(function(){
       echo "hi!\n";
}, 1000);

Example 2: setinterval php

function setInterval($f, $milliseconds)
{
       $seconds=(int)$milliseconds/1000;
       while(true)
       {
           $f();
           sleep($seconds);
       }
}