<?
error_reporting(-1);
$dataString="test='a,b,c=1,d'";
$resultArray=array();
$explodedByComma=explode(',', $dataString);
foreach($explodedByComma as $string){
    $string=trim($string);
	$explodedByEqual=explode('=', $string);
	$key=$explodedByEqual[0];
	$value=$explodedByEqual[1];
	$resultArray[$key]=$value;
}
var_dump($resultArray);
?>