ช่วยด้วยครับ การ join string ใน array ขอบคุณท่านกูรูล่วงหน้าครับ มึนมาหลายวันแล้ว

<?php
$arr = array("1,2","1,3","3,4","4,2");
$value=summary($arr[0],$arr[1]);
print_r($value);
function summary($str1,$str2){
	$str1=explode(",",$str1);
	$str2=explode(",",$str2);
	$result = array_merge_recursive($str1, $str2);
	$diff=array_unique($result);
	sort($diff);
	return $diff;
}
?>

$arr = array("1,2","1,3","3,4","4,2");

function unique_merge(){
	$size = func_num_args();
	
	for($i=0; $i < $size; $i++){
		$arg = func_get_arg($i);
		$tmp = preg_split('/,/', $arg);
		
		$arr = array_merge($arr, $tmp);
	}
	
	$arr = array_unique($arr);
	sort($arr);
	$arr = join(',', $arr);

	return $arr;
}

echo unique_merge($arr[0], $arr[1]), '<br>';
echo unique_merge($arr[0], $arr[2]), '<br>';
echo unique_merge($arr[1], $arr[3], $arr[0]), '<br>';

$arr = array("1,2","1,3","3,4","4,2");
$obj=new probability_merge;
$obj->set($arr);
$process =$obj->get_prob();
$result=$obj->get_prob_merge();
echo "วิธีการคือ <BR>";
foreach($process as $p){
	echo $p."<BR>";
}
echo "ผลลัพธ์:<BR>";
foreach($result as $r){
	echo $r."<BR>";
}

class probability_merge{
	 static  $prob=array();
	 static $prob_merge=array();
	 public function set($array){
			self::probability($array,count($array));
	 }
	public static function probability($array,$loop){
		$offset =count($array)-$loop ;
		for($i=($offset+1); $i<count($array);$i++){
			self::merge($array[$offset].",".$array[$i]);
			self::$prob[]=$array[$offset]."+".$array[$i];
		}
		if($offset!=count($array)){
			self::probability($array,$loop-1);		
		}
	}
	public static function merge($subject){
			$arr=preg_split('/,/',$subject);
			$arr=array_unique($arr);
			sort($arr);
			self::$prob_merge[]=join(",",$arr);									
	}
	public function get_prob(){
		return self::$prob;
	}
	public function get_prob_merge(){
		return self::$prob_merge;
	}
 }