PHP Performance Tuning Timing Program Execution by Statement

PHP Performance Tuning

Timing Program Execution by Statement

Problem

You have a block of code and you want to profile it to see how long each statement takes to execute.

Solution

Use the declare construct and the ticks directive:

       function profile($display = false) {

              static $times;

          

              switch ($display) {

              case false:

                     // add the current time to the list of recorded times

                     $times[] = microtime();

                     break;

              case true:

                     // return elapsed times in microseconds

                     $start = array_shift($times);

       

                     $start_mt = explode(' ', $start);

                     $start_total = doubleval($start_mt[0]) + $start_mt[1];

       

                     foreach ($times as $stop) {

                            $stop_mt = explode(' ', $stop);

                            $stop_total = doubleval($stop_mt[0]) + $stop_mt[1];

                            $elapsed[] = $stop_total - $start_total;

                     }

                     unset($times);

                     return $elapsed;

                     break;

              }

       }

       // register tick handler

       register_tick_function('profile');

       

       // clock the start time

       profile();

       // execute code, recording time for every statement execution

       declare (ticks = 1) {

              foreach ($_SERVER['argv'] as $arg) {

                     print "$arg: " . strlen($arg) ."\n";

              }

       }

       // print out elapsed times

       print "---\n";

       $i = 0;

       foreach (profile(true) as $time) {

              $i++;

              print "Line $i: $time\n";

       }

Discussion

The ticks directive allows you to execute a function on a repeatable basis for a block of code. The number assigned to ticks is how many statements go by before the functions that are registered using register_tick_function() are executed.

In the Solution, we register a single function and have the profile() function execute for every statement inside the declare block. If there are two elements in $_SERVER['argv'], profile() is executed six times: once when the clocks starts; twice for the two times through the foreach loop; another two when the print strlen($arg) line is executed; and finally, once when foreach returns false:

       Line 1: 5.3882598876953E-5

       Line 2: 5.6982040405273E-5

       Line 3: 6.2942504882812E-5

       Line 4: 6.5803527832031E-5

       Line 5: 6.7949295043945E-5

       Line 6: 6.9856643676758E-5

You can also set things up to call two functions every three statements:

       register_tick_function('profile');

       register_tick_function('backup');

       declare (ticks = 3) {

              // code...

       }

You can also pass additional parameters into the registered functions, which can be object methods instead of regular functions:

       // pass "parameter" into profile()

       register_tick_function('profile', 'parameter');

       // call $car->drive();

       $car = new Vehicle;

       register_tick_function(array($car, 'drive'));

If you want to execute an object method, pass the object and the name of the method encapsulated within an array. This lets the register_tick_function() know you’re referring to an object instead of a function.

Call unregister_tick_function() to remove a function from the list of tick functions:

       unregister_tick_function('profile');