- microtime: documentation ( source)
<?php
// The original function
function a($i){$e=microtime(1)+$i;while(microtime(1)<$e);}
// Use 'for' instead of 'while'
function b($i){for($e=microtime(1)+$i;microtime(1)<$e;);}
// Extract 'microtime' into a variable
// Requires error_reporting(0) to suppress the "PHP Notice: Use of undefined constant microtime"
// Use '-d error_reporting=0' in the command line
function c($i){for($f=microtime,$e=$f(1)+$i;$f(1)<$e;);}
// Squeeze the initialization of $f into its first use
// PHP 7 only; it doesn't compile on older versions
function d($i){for($e=($f=microtime)(1)+$i;$f(1)<$e;);}