SqlHelper::execute_dml PHP Method

public  function execute_dml($sql){

$b=mysql_query($sql,$this->conn) or die(mysql_error());
if(!$b){
return 0; //失败
}else{
if(mysql_affected_rows($this->conn)>0){
return 1;//表示执行ok
}else{
return 2;//表示没有行受到影响
}
}

}

function addMessage($sender,$getter,$con) {
//创建SQL语句
$sql="insert into messages (sender,getter,content,sendTime) values('$sender','$getter','$con',now())";
file_put_contents("/Library/WebServer/Documents/ajax/mylog.txt",$sql."\r", FILE_APPEND);
$sqlHelper=new SqlHelper();
 return $sqlHelper->execute_dml($sql);
}