str_replace on steroids

str_map.php

<?php

namespace NorthernLights\Util;

/**
 * Map/replace string accordingly to supplied character map
 * Note:
 *       There is certain overhead because we use 4 function calls main -> mapper -> array_keys -> array_values
 *       versus that it can be done with just single str_replace()
 *       However, accordingly to benchmarks, difference becomes noticeable only after 1 000 000 iterations (~300ms slower)
 *
 * @param string $subject
 * @param array $replMap
 *   - Schema: "target" => "replacement"
 *
 * @param callable|null $mapper
 *   - Mapper function. Must accept arguments array, array, string and return string
 *   - Default mapper function is str_replace
 *
 * @author Aleksandar Puharic <xzero@elite7hackers.net>
 *
 * @return string
 */
function strMap($subject, array $replMap, callable $mapper = null)
{
    // Return immediately if empty
    if ($subject === '') {
        return '';
    }

    // Return immediately if empty
    if ($replMap === []) {
        return $subject;
    }

    $mapper = ($mapper === null) ? 'str_replace' : $mapper;

    return $mapper(
        array_keys($replMap),
        array_values($replMap),
        $subject
    );
}

Usage:

<?php

use function NorthernLights\Util\strMap;

$test = strMap('Hello {{you}}! It\'s a {{weekday}} today.', [
            '{{you}}' => 'world',
            '{{weekday}}' => date('l')
]);

var_dump($test);

Example above shows something like "Hello world! It's a Sunday today."
Note: Wrapping in {{string}} is not required.
It will work like standard str_replace unless different callable is supplied.

Doing exactly the same with str_replace(), yields quite ugly code:

<?php

$test = str_replace([
    '{{you}}',
    '{{weekday}}'
], [
    'world',
    date('l')
], 'Hello {{you}}! It\'s a {{weekday}} today.');

var_dump($test);

To make the code more readable, I could have assigned arrays to variables, but that's impractical, and would yield anything but elegant code.