Converts an Array to comma seperated string

ArrayToCommaSeperatedString.php

<?php

function arrayToCommaSeperatedString($arr,$key=null){
    $str = '';
    
    if(is_null($key))
      return $str;
    
    foreach($arr as $arr_ele){
        $str .= $$arr_ele[$key].", ";
    }

    return rtrim($str_authors,', ');
}