A php slug function from https://ourcodeworld.com/articles/read/253/creating-url-slugs-properly-in-php-including-transliteration-support-for-utf-8

shorter-slugify.php

<?php 

function Slug($string){
    return strtolower(trim(preg_replace('~[^0-9a-z]+~i', '-', html_entity_decode(preg_replace('~&([a-z]{1,2})(?:acute|cedil|circ|grave|lig|orn|ring|slash|th|tilde|uml);~i', '$1', htmlentities($string, ENT_QUOTES, 'UTF-8')), ENT_QUOTES, 'UTF-8')), '-'));
}

$user = 'Cómo hablar en sílabas';
echo Slug($user); // como-hablar-en-silabas

$user = 'Álix Ãxel';
echo Slug($user); // alix-axel

$user = 'Álix----_Ãxel!?!?';
echo Slug($user); // alix-axel

slug.php

<?php


public function slugify($text)
{
    // replace non letter or digits by -
    $text = preg_replace('~[^\pL\d]+~u', '-', $text);

    // transliterate
    $text = iconv('utf-8', 'us-ascii//TRANSLIT', $text);

    // remove unwanted characters
    $text = preg_replace('~[^-\w]+~', '', $text);

    // trim
    $text = trim($text, '-');

    // remove duplicate -
    $text = preg_replace('~-+~', '-', $text);

    // lowercase
    $text = strtolower($text);

    if (empty($text)) {
        return 'n-a';
    }

    return $text;
}