Replace multiple parts of a string at once using `mb_ereg_replace`.

mb_ereg_bulk_replace.php

<?php
/**
 * It let you do what you can do with `preg_replace` with `mb_ereg_replace`.
 *
 * replacing multiple strings at once.
 *
 * @param array $pattern
 * @param array $replacement
 * @param $string
 *
 * @return bool|string
 */
$mb_ereg_bulk_replace = function ($pattern, $replacement, $string) {
	if (count($pattern) !== count($replacement)) {
		return false;
	} else {
		$replace_rule = array_combine($pattern, $replacement);
		return array_reduce($pattern, function ($string, $v) use ($replace_rule) {
			$string = mb_ereg_replace($v, $replace_rule[$v], $string);
			return $string;
		}, $string);
	}
};

This is far from a 1:1 of preg_replace. But you did get me started toward something closer.

       $mb_ereg_bulk_replace = function ($patterns, $replacements, $string) {
		$patterns     = is_string($patterns) ? [$patterns] : $patterns;
		$replacements = is_string($replacements) ? [$replacements] : $replacements;
		$options = [];
		foreach ($patterns as $key => $pattern) {
			$pattern = explode('/', $pattern);
			$optionString = array_pop($pattern);
			$options[] = empty($optionString) ? null : $optionString;
			array_shift($pattern);
			$patterns[$key] = implode('/', $pattern);
			$replacements[$key] = isset($replacements[$key]) ? $replacements[$key] : "";
		}
		$replace_rule = array_combine($patterns, $replacements);
		$options = array_combine($patterns, $options);
		return array_reduce($patterns, function ($string, $v) use ($replace_rule, $options) {
			return mb_ereg_replace($v, $replace_rule[$v], $string, $options[$v]);
		}, $string);
	};

Note that some supplied modifiers might not be available in mb_ereg_replace, namely u (as it was/is unnecessary).

Encoding safe string sanitation is built into Elleus where I used this function.

Side note. mb_ereg_replace does not accept appended and pre-pended "/ /" slashes Modifiers and this script I've posted here only handles the slash version of modifiers that can be used with preg_replace.