setInterval in PHP

JavaScript has a native method for executing a function periodically: setInterval. But in PHP, it’s a little bit harder. PHP lacks a setInterval equivalent. The closest we can get are the sleep(), usleep(), and time_nanosleep() functions. These functions delay script execution by a certain period of time (either seconds, microseconds, or a combination or seconds and nanoseconds).

PHP does, however, have a means of executing code as long as a condition is true: the while loop. What we can do, then is combine a while loop with one of the sleep functions — in this case usleep() — to create a setInterval equivalent. Check out the code below.

function setInterval($func = null, $interval = 0, $times = 0){
  if( ($func == null) || (!function_exists($func)) ){
    throw new Exception('We need a valid function.');
  }

  /*
  usleep delays execution by the given number of microseconds.
  JavaScript setInterval uses milliseconds. microsecond = one
  millionth of a second. millisecond = 1/1000 of a second.
  Multiplying $interval by 1000 to mimic JS.
  */

  $seconds = $interval * 1000;

  /*
  If $times > 0, we will execute the number of times specified.
  Otherwise, we will execute until the client aborts the script.
  */

  if($times > 0){

    $i = 0;

    while($i < $times){
        call_user_func($func);
        $i++;
        usleep( $seconds );
    }
  } else {

    while(true){
        call_user_func($func); // Call the function you've defined.
        usleep( $seconds );
    }
  }
}

function doit(){
  print 'done!<br>';
}

To invoke, do something similar to the following.

setInterval('doit', 5000); // Invoke every five seconds, until user aborts script.

setInterval('doit', 1000, 100); // Invoke every second, up to 100 times.

Here’s the catch: no data will be sent to the browser until the script has completely executed.