escape_mb_chars.php

<?php

$testString = "• janky • stuff • take me away ••";

function escape_mb_chars($str) {
  $first = preg_replace_callback('/\p{C}/u', function ($m) {
    $char = current($m);
    return substr(json_encode($char), 1, -1);
  }, $str);
  return rtrim($first, '\n');
}

function clean_string($str) {
  return preg_replace('/[^a-zA-Z0-9\s]/', '', $str);
}


print clean_string($testString) . "\n";