- var_dump: documentation ( source)
- preg_match_all: documentation ( source)
- implode: documentation ( source)
<?php
$foo = "▒▒▒Y#CzdU▒BB▒(ȅi▒](▒▒▒▒W▒dv▒▒6m▒▒▒~▒▒▒{A։9fI΄#`I▒▒Q▒▒▒o▒▒tE▒▒]▒'J▒▒ `▒*q▒▒X}▒▒▒▒)P{▒-hs▒▒Uz▒6▒i▒▒▒J▒I";
preg_match_all('([a-zA-Z0-9]{1})', $foo, $matches);
var_dump(implode($matches));