Function to generate a slug (a normalized URL sanitized string)

composer.json

{
    "name": "attitude/generate_slug",
    "autoload": {
        "files": ["function-generate_slug.php"]
    }
}

function-generate_slug.php

<?php
 
/**
 * Function to generate a slug (a normalized URL sanitized string)
 * 
 * Turns 'Any impressive headline' to 'any-impressive-headline'
 *
 * @param   string $str     String to use to generate slug
 * @return  string          Returns slug
 * @author                  internet
 * @license                 public domain
 *
 */
function generate_slug($str)
{
    setlocale(LC_ALL, 'en_US.UTF8');

    $r = '';
    $str = iconv('UTF-8', 'ASCII//TRANSLIT', $str);

    for ($i = 0; $i < strlen($str); $i++) {
        $ch1 = $str[$i];
        $ch2 = mb_substr($str, $i, 1);
        $r .= $ch1 == '?' ? $ch2 : $ch1;
    }

    $str = str_replace(
        array('&auml;', '&ouml;', '&uuml;', '&szlg', '&amp;', ' & ', '&', ' - ', '/', ' / ', ' ', '='),
        array('ae', 'oe', 'ue', 'ss', '-and-', '-and-', '-and-', '-', '-', '-', '-', '-'),
        strtolower($r)
    );

    $chars = "abcdefghijklmnopqrstuvwxyz0123456789_-";
    $replace = '';

    for ($i=0; $i<strlen($str); $i++) {
        if (false !== strpos($chars, $str[$i])) {
            $replace .= $str[$i];
        }
    }

    return $replace;
}