Understanding PHP microtime() Function and Measuring Execution Time

The microtime() function returns the current Unix timestamp together with microseconds. When called without arguments it returns a string in the format "msec sec", where sec is the number of seconds since the Unix epoch and msec is the microsecond part.

If the optional boolean parameter $get_as_float is set to true, the function returns a float representing the full timestamp (seconds plus fractional microseconds).

Below is a practical example that defines a microtime_float() helper to obtain a float timestamp, measures the time taken by a short operation, and outputs the elapsed time.

<?php
/**
 * Simple function to replicate PHP 5 behaviour
 */
function microtime_float()
{
    list($usec, $sec) = explode(" ", microtime());
    return ((float)$usec + (float)$sec);
}

$time_start = microtime_float();
// Sleep for a while
usleep(100);
$time_end = microtime_float();
$time = $time_end - $time_start;

echo "Did nothing in $time seconds
";
?>

The script records the start time, pauses execution for 100 microseconds with usleep(), records the end time, calculates the difference, and prints the elapsed time, demonstrating how to use microtime() for performance measurement.