/**
 * Compute the delay to execute a function a number of time
 * @param $count Number of time that the tests will execute the given function
 * @param $function  the function to test. Can be a string with parameters (ex: 'myfunc(123, 0, 342)') or a callback
 * @return float   Duration in seconds (as a float)
 */
function timeit($count, $function) {
 if ($count <= 0){
  echo "Error: count have to be more than zero";
  return -1;
 }
 $nbargs = func_num_args();
 if ($nbargs < 2) {
  echo 'Error: No Funciton!';
  echo 'Usage:';
  echo "\ttimeit(count, 'function(param)')";
  echo "\te.g:timeit(100, 'function(0,2)')";
  return -1;      // no function to time
 }
 // Generate callback
 $func = func_get_arg(1);
 $func_name = current(explode('(', $func));
 if (!function_exists($func_name)) {
  echo 'Error: Unknown Function';
  return -1;     // can't test unknown function
 }
 $str_cmd = '';
 $str_cmd .= '$start = microtime(true);';
 $str_cmd .= 'for($i=0; $i<'.$count.'; $i++) '.$func.';';
 $str_cmd .= '$end = microtime(true);';
 $str_cmd .= 'return ($end - $start);';
 return eval($str_cmd);
}

//取平方根
function sqrt_nd($num){
 $value = $num;
 while(abs($value*$value -$num) > 0.001){
  $value = ($value + $num/$value)/2;
 }
 return $value;
}
print timeit(1000, 'sqrt_nd(5)');
print "\n";
print timeit(1000, 'sqrt(5)');

<?php
$start_time = microtime(true);
for($i=1;$i<=1000;$i++){
echo $i.'<br>';
}
$end_time = microtime(true);