Performance test strtr vs str_replace

strtr-vs-str_replace.php

<?php

$iterations = 10000000;
$defaultString = 'Test string m8';
$replaceTpl = 'm8';
$placeholder = 'is more effective';

$start = microtime(true);
for ($i = 0; $i < $iterations; ++$i) {
    $out = str_replace($replaceTpl, $placeholder, $defaultString);

}
$time = microtime(true) - $start;
echo 'Str_Replace scalars: ' . $time . "\n";

$start = microtime(true);
for ($i = 0; $i < $iterations; ++$i) {
    $out = str_replace([$replaceTpl], $placeholder, $defaultString);

}
$time = microtime(true) - $start;
echo 'Str_Replace search array, replace scalar: ' . $time . "\n";

$start = microtime(true);
for ($i = 0; $i < $iterations; ++$i) {
    $out = str_replace([$replaceTpl], [$placeholder], $defaultString);

}
$time = microtime(true) - $start;
echo 'Str_Replace search array, replace array: ' . $time . "\n";

$start = microtime(true);
for ($i = 0; $i < $iterations; ++$i) {
    $out = strtr($defaultString, $replaceTpl, $placeholder);

}
$time = microtime(true) - $start;
echo 'Strtr 3 arguments: ' . $time . "\n";

$start = microtime(true);
for ($i = 0; $i < $iterations; ++$i) {
    $out = strtr($defaultString, [$replaceTpl => $placeholder]);

}
$time = microtime(true) - $start;
echo 'Strtr 2 arguments: ' . $time . "\n";

PHP 7.2.4-1+ubuntu16.04.1+deb.sury.org+1 (cli) (built: Apr 5 2018 08:53:57) ( NTS ) Copyright (c) 1997-2018 The PHP Group Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies with Zend OPcache v7.2.4-1+ubuntu16.04.1+deb.sury.org+1, Copyright (c) 1999-2018, by Zend Technologies

Str_Replace scalars: 0.69700789451599
Str_Replace search array, replace scalar: 1.101686000824
Str_Replace search array, replace array: 1.4618530273438
Strtr 3 arguments: 1.987979888916
Strtr 2 arguments: 1.0328650474548

The "Strtr 3 arguments" use is incorrect. See documentation:

If given three arguments, this function returns a copy of string where all occurrences of each (single-byte) character in from have been translated to the corresponding character in to, i.e., every occurrence of $from[$n] has been replaced with $to[$n], where $n is a valid offset in both arguments.

Maybe an example would help understand better: strtr('baab', 'ab', '01') returns 1001.