<?php
$text = "а, аб, ба";
$iu = mb_strlen($text);
$arr_text = ["й" => 2, "ц" => 4, "у" => 6, "к" => 8, "е" => 10, "н" => 12, "г" => 14, "ш" => 16, "щ" => 18, "з" => 20, "х" => 22, "ф" => 24, "ы" => 26, "в" => 28, "а" => 30, "п" => 32, "р" => 34, "о" => 36, "л" => 38, "д" => 40, "ж" => 42, "э" => 44, "я" => 46, "ч" => 48, "с" => 50, "м" => 52, "и" => 54, "т" => 56, "ь" => 58, "б" => 60,  "ю" => 60, " " => 62, "," => 64];
$text_split = mb_str_split($text);
foreach($text_split as $tt){
 $uu = $arr_text[$tt] * $iu.":";
 $ru = $uu;
 echo $ru;
 }
 ?>