Calculate the process runtime in PHP

runtime.php

<?php
$process_start_time;
$process_end_time;
$process_runtime;

// Capture process start time
list($usec, $sec) = explode(' ', microtime());
// Store the start time
$process_start_time = (float) $sec + (float) $usec;

// Capture process end time
list($usec, $sec) = explode(' ', microtime());
// Store the end time
$process_end_time = (float) $sec + (float) $usec;

// Calculate process runtime
$process_runtime = round($process_end_time - $process_start_time, 5);