Check if adding strpos and strrpos is worth it

bench.php

<?php

// define benchmarked functions

$f1 = function ($string) {
    for ($i = 0, $count = strlen($string); $i < $count; $i++) {
        if ($string[$i] === '*') {
            $string[$i]= mt_rand(0, 1) ? '#' : '?';
        }
    }
};

$f2 = function ($string) {
    if (($pos = strpos($string, '*')) !== false) {
        for ($i = $pos, $count = strlen($string); $i < $count; $i++) {
            if ($string[$i] === '*') {
                $string[$i] = mt_rand(0, 1) ? '#' : '?';
            }
        }
    }
};

$f3 = function ($string) {
    if (($pos = strpos($string, '*')) !== false) {
        for ($i = $pos, $count = strrpos($string, '*', $pos); $i < $count; $i++) {
            if ($string[$i] === '*') {
                $string[$i] = mt_rand(0, 1) ? '#' : '?';
            }
        }
    }
};

// setup benchmark params

$iterations = 100000;
$arguments = array(
    'has' => array('#############****??????????????????'),
    'hasnt' => array('###############????????????????????'),
);
$functions = array(
    'none'         => $f1,
    'strpos'          => $f2,
    'strrpos'          => $f3,
);
$checkValues = false;

// run benchmark

$benchmark = function ($callable, $arguments, $iterations = 100000) {
    $start_time = microtime(TRUE);

    for($i = 0; $i < $iterations; $i++) {
        $value = call_user_func_array($callable, $arguments);
    }

    $end_time = microtime(TRUE);

    $total_time = $end_time - $start_time;

    return array($value, $total_time);
};

$results = array();
$previous = null;
foreach($arguments as $arguments_name => $argument) {
    foreach($functions as $function_name => $function) {
        list($value, $time) = $benchmark($function, $argument);
        if ($checkValues && $previous !== null && $previous !== $value) {
            echo "error: $function_name ($arguments_name) returned different results:\n";
            var_dump($previous, $value);
        }
        $previous = $value;

        $results[$function_name] = $time;
    }
    // print results

    asort($results);
    $min_time = reset($results);

    echo "$arguments_name:\n";
    foreach($results as $name => $time) {
        echo str_pad($name.": ", 25, ' ', STR_PAD_LEFT).$time.' ('.(number_format(100*$time/$min_time, 2)).'%)'."\n";
    }
}

echo "\nPerformed $iterations iterations.\n\n";

bench2.php

<?php

require_once 'src/autoload.php';
$faker = Faker\Factory::create();

// define benchmarked functions

$f1 = function ($string) use ($faker) {
    preg_replace_callback('/\?/u', [$faker, 'randomLetter'], $string);
};

$f2 = function ($string) use ($faker) {
    if (($pos = strpos($string, '?')) !== false) {
        for ($i = $pos, $last = strrpos($string, '?', $pos); $i < $last; $i++) {
            if ($string[$i] === '?') {
                $string[$i] = $faker->randomLetter();
            }
        }
    }
};

// setup benchmark params

$iterations = 100000;
$arguments = array(
    'mixed' => array('#############****??????????????????'),
    'only' => array('????????????????????'),
);
$functions = array(
    'preg_replace'    => $f1,
    'strpos'          => $f2,
);
$checkValues = false;

// run benchmark

$benchmark = function ($callable, $arguments, $iterations = 100000) {
    $start_time = microtime(TRUE);

    for($i = 0; $i < $iterations; $i++) {
        $value = call_user_func_array($callable, $arguments);
    }

    $end_time = microtime(TRUE);

    $total_time = $end_time - $start_time;

    return array($value, $total_time);
};

$results = array();
$previous = null;
foreach($arguments as $arguments_name => $argument) {
    foreach($functions as $function_name => $function) {
        list($value, $time) = $benchmark($function, $argument);
        if ($checkValues && $previous !== null && $previous !== $value) {
            echo "error: $function_name ($arguments_name) returned different results:\n";
            var_dump($previous, $value);
        }
        $previous = $value;

        $results[$function_name] = $time;
    }
    // print results

    asort($results);
    $min_time = reset($results);

    echo "$arguments_name:\n";
    foreach($results as $name => $time) {
        echo str_pad($name.": ", 25, ' ', STR_PAD_LEFT).$time.' ('.(number_format(100*$time/$min_time, 2)).'%)'."\n";
    }
}

echo "\nPerformed $iterations iterations.\n\n";