This function returns the current Unix timestamp with microseconds. This function is only available on operating systems that support the gettimeofday() system call.
Optional. When called without the optional argument, this function returns the string "msec sec" where sec is the current time measured in the number of seconds since the Unix Epoch (0:00:00 January 1, 1970 GMT), and msec is the microseconds part. If the optional get_as_float is set to TRUE then a float (in seconds) is returned.
Explained in Definition.
Following is the usage of this function:
$time_start = microtime(true);
// Sleep for a while
$time_end = microtime(true);
$time = $time_end - $time_start;
echo "Did nothing in $time seconds\n";