Test program execution time in PHP

usually in order to estimate the execution time of a more complex program or to compare the execution efficiency of a scenario in a variety of scenarios, we need to calculate the time it takes for the program to execute, with the following code:

$start _time = Microtime (true);            Gets the time that the program started executing $end_time = Microtime (true);   Gets the time that the program execution ended $exec_time = $end _time-$start _time; Calculate the difference echo $exec _time;