[ขอคำแนะนำครับ] สอบถามเรื่อง split string to array แล้วเช็คเงื่อน หาผลรวม

function mb_str_split( $string ) { 
    return preg_split('/(?<!^)(?!$)/u', $string ); 
} 
$array = mb_str_split("1ธณ7890");

if(sort($array)){
	foreach($array as $key=>$value){
		 if(ereg("(ฉ|ณ|ฌ|น|ม|ห|ฮ|ฎ|ฬ)", $value)==1){ $value2[]="5";}
		 else if(ereg("(ค|ธ|ร|ญ|ษ)", $value)==1){ $value2[]="4";}
		 else {$value2[]=$value;}
	}
}

if(sort($value2)){
	foreach($value2 as $key=>$value){
		echo '['.$value2.'] = '.$value.'<br />';
	}
}

echo "sum=".array_sum($value2) . "<br />";