Change any string into SEO friendly URL slug

seo-slug.php

<?php
// example code

setlocale(LC_CTYPE, 'cs_CZ');

$str = "Běloučký kůň úpěl ďábelské ódy $   ' 1234";

print
  preg_replace('/(?<=-)-+/', '',                   // Replace all duplicase hyphens with one only
    preg_replace( '/[^-a-z0-9]/', '',              // Strip all non-alfanumeric characters or hyphens
      strtr(                                       // Replace spaces with hyphens
        strtolower(                                // Transform to lowercase
	  iconv('UTF-8', 'ASCII//TRANSLIT', $str)  // Transliterate to ASCII
        ),
        [" " => "-"]
      )
    )
  )
;

// Expected output:
// beloucky-kun-upel-dabelske-ody-1234