<?php
$arraystring = ['cat','test','catty', 'meow'];
$substring = 'c';
filter($arraystring,$substring);
function filter ($arraystring,$substring){
    $resultarray = array();
    foreach ($arraystring as  $substringwords) {
        $checkSubstring = sub($substringwords,$substring);
        if ($checkSubstring){
            $resultarray[] = $substringwords;
        } else {
            echo $substring. " "."not found in"." ".$arraystring;
        }
    }

    return $resultarray;
}

function sub($substringwords,$substring){
   $array = array();
   $indexofarray = 0;
    for ($i = 0; $i <strlen($substringwords); $i++) {
        for ($j = 0;$j < strlen($substring);$j++){
            if ($substringwords[$i] == $substring[$j])  {
                    $array[] = $substring;
                $indexofarray++;
            }
        }
    }
    if (empty($array)) {

        return false;
    } else {
    return true ;
}
}
var_dump(filter($arraystring,$substring));