testing pass by reference vs. pass by value

passbyreferencetest

PHP Version 5.4.29

--------------------------------------------------
Testing large_array over 100,000 iterations:

pass_by_ref                   95.081090927124 ms
pass_by_val                   86.126089096069 ms
--------------------------------------------------
Testing small_array over 100,000 iterations:

pass_by_ref                   86.638927459717 ms
pass_by_val                   85.745096206665 ms
--------------------------------------------------
Testing large_object over 100,000 iterations:

pass_by_ref                   86.174964904785 ms
pass_by_val                   88.841915130615 ms
--------------------------------------------------
Testing large_string over 100,000 iterations:

pass_by_ref                   80.765962600708 ms
pass_by_val                   81.165075302124 ms
--------------------------------------------------
Testing small_string over 100,000 iterations:

pass_by_ref                   85.597038269043 ms
pass_by_val                   83.338022232056 ms
--------------------------------------------------
Testing integer over 100,000 iterations:

pass_by_ref                   84.825038909912 ms
pass_by_val                   81.841945648193 ms

--------------------------------------------------
               average (ms)        total (ms)
--------------------------------------------------
pass_by_ref    86.513837178548     519.08302307129
pass_by_val    84.50969060262      507.05814361572

passbyreferencetest.php

<?php

$iterations = 100000;

$large_array = array_fill(PHP_INT_MAX / 2, 1000, 'a');

$values = [
    'large_array'  => $large_array,
    'small_array'  => array('this', 'is', 'a', 'small', 'array'),
    'large_object' => (object)$large_array,
    'large_string' => str_repeat('a', 100000),
    'small_string' => 'this is a small string',
    'integer'      => PHP_INT_MAX / 2,
];

$totals = [
    'pass_by_ref' => 0,
    'pass_by_val' => 0,
];

function pass_by_ref(&$var) {}

function pass_by_val($var) {}

echo "PHP Version ".phpversion()."\n\n";

foreach ($values as $name => $value) {
    echo str_repeat('-', 50)."\n";

    echo "Testing {$name} over ".number_format($iterations)." iterations:\n\n";

    $start = microtime(true);

    for ($i = 0; $i < $iterations; $i++) {
        pass_by_ref($value);
    }

    $end = microtime(true);

    $duration = ($end - $start) * 1000;

    $totals['pass_by_ref'] += $duration;

    echo str_pad('pass_by_ref', 30)."{$duration} ms\n";

    //-----------------------------------------------------------------------------

    $start = microtime(true);

    for ($i = 0; $i < $iterations; $i++) {
        pass_by_val($value);
    }

    $end = microtime(true);

    $duration = ($end - $start) * 1000;

    $totals['pass_by_val'] += $duration;

    echo str_pad('pass_by_val', 30)."{$duration} ms\n";

    //-----------------------------------------------------------------------------
}

echo "\n".str_repeat('-', 50)."\n";
echo str_pad('', 15);
echo str_pad('average (ms)', 20);
echo str_pad('total (ms)', 20)."\n";
echo str_repeat('-', 50)."\n";

foreach ($totals as $name => $total) {
    echo str_pad($name, 15);
    echo str_pad($total/count($values), 20);
    echo str_pad($total, 20)."\n";
}

echo "\n";