Cut-and-paste benchmarking library with baseline compensation and weighted averages

bench.php

<?php

header('Content-type: text/plain');

define('NUM_RUNS', 200); // total number of runs/readings
define('NUM_LOOP', 100); // number of iterations per run

// benchmark a function using various PHP features to establish
// a performance baseline for the PHP version / platform / etc.:

$baseline = bench(function() {
    $n = 12345.12345;
    $s = str_repeat('0123456789', 10);

    $s1 = substr($s, 0, 20);
    $s2 = substr($s, 10, 40) . $s1;
    $s3 = substr($s, 20, 20) . $s2;
    $s4 = substr($s3, 20, 40);
    
    $n1 = floor($n);
    $n2 = round($n);
    $n3 = sin($n);
    $n4 = cos($n);
    
    $a = array('foo'=>100, 'bar'=>200, 'baz'=>300);
    $e = '{"foo":100,"bar":200,"baz":300}';
    
    $j = json_encode($a);
    $d = json_decode($e, true);

    if ($a !== $d) die('internal error (1)');
    if ($e !== $j) die('internal error (2)');
    
    $a1 = $a['foo'];
    $a2 = $a['bar'];
    $a3 = $a['baz'];
    
    $x1 = parse_url('scheme://domain:port/path?query_string#fragment_id');
    $x2 = preg_match('/(?P<name>\w+): (?P<digit>\d+)/', 'foobar: 2008', $matches);
    $x3 = date('Y-m-d H:i:s', strtotime('2014-02-13 09:36:27'));
    $x4 = sha1('abcdefghijklmnopqrstuvwxyz', $x3);
});

echo "BASELINE = " . number_format(1000*$baseline, 3) . " msec\n";

echo PHP_OS . "\n";

echo PHP_VERSION . "\n";

echo NUM_RUNS . " test runs\n\n";

function bench($func) {
    $time = array();
    
    for ($i=0; $i<=NUM_RUNS; $i++) {
        $start = microtime(true);
        for ($n=0; $n<NUM_LOOP; $n++) {
            $func();
        }
        $end = microtime(true);
        
        $time[$i] = ($end - $start) * 1000 / NUM_LOOP;
    }
    
    unset($time[0]); // ignore the first reading (usually inaccurate)
    
    return weighted_average($time);
}

function mark($text, $func) {
    $time = bench($func);
    echo "* " . str_pad($text . ' ', 40, '.')
        . str_pad(' ' . number_format(($time*1000), 3) . ' msec ', 20, '.', STR_PAD_LEFT)
        . str_pad(' ' . number_format(($time*1000/$GLOBALS['baseline']), 3) . ' points', 20, '.', STR_PAD_LEFT) . "\n";
}

function weighted_average($values) {
    $sum = 0;
    foreach ($values as $i => $value) {
        $sum += $value;
    }
    
    $avg = $sum / count($values);

    $error = array();
    
    $max_error = 0;
    
    foreach ($values as $i => $value) {
        $error[$i] = abs($avg - $value);
        $max_error = max($error[$i], $max_error);
    }
    
    $total_weight = 0;
    $weighted_sum = 0;
    
    foreach ($values as $i => $value) {
        $weight = 1 - ($error[$i] / $max_error);
        $weight = $weight * $weight; // square
        $total_weight += $weight;
        $weighted_sum += $weight * $value;
    }
    
    $weighted_average = $weighted_sum / $total_weight;
    
    return $weighted_average;
}

// Now benchmark your functions like this:

mark(
    'Building a string',
    function () {
        $foo = 'foo';
        $foo .= 'bar';
        $foo .= 'baz';
    }
);

Packaged version here.