مشکل در security

سلام

کلاس DB رو طبق آموزشهای استاد تغییر دادم ولی با این ارور مواجه شدم

ممنون می شم بررسی کنید

<?
class Db{
  private $connection;
  private static $db;
  public static function getInstance($option=null){
    if(self::$db==null){
      self::$db=new Db($option);
    }
    return self::$db;
  }
  private function __construct($option=null){
    if($option!=null){
      $host=$option['host'];
      $user=$option['user'];
      $pass=$option['pass'];
      $name=$option['name'];
    }else{
      global $config;
      $host = $config['db']['host'];
      $user = $config['db']['user'];
      $pass = $config['db']['pass'];
      $name = $config['db']['name'];
    }
    $this->connection = new mysqli($host, $user, $pass, $name);
    if ($this->connection->connect_error) {
      echo ("Connection failed due to: " . $this->connection->connect_error);
      exit;
    }

    $this->connection->query("SET NAMES 'utf8'");
  }
  private function safeQuery(&$sql,$data){
    foreach ($data as $key=>$value){
      $value=$this->connection->real_escape_string($value);
      $value="'$value'";
      $sql=str_replace("<-$key->",$value,$sql);
    }
    $this->connection->query($sql);

  }
  public function insert($sql,$data=array()){
    $result=$this->safeQuery($sql,$data);
    if(!$result){
      echo "Your query was ".$sql." Faild! Cause: ".mysql_error($this->connection());
      exit;
    }

    return $result;
  }
  public function modify($sql,$data=array()){
    $result=$this->csafeQuery($sql,$data);
    if(!$result){
      echo "Your query was ".$sql." Faild! Cause: ".mysql_error($this->connection());
      exit;
    }
    return $result;
  }
  public function first($sql,$data=array()){
    $records=$this->query($sql,$data);
    if($records==null){
      return null;
    }
    return $records[0];
  }
  public function query($sql,$data=array()){
    $result=$this->safeQuery($sql,$data);
    if(!$result){
      echo "Your query was ".$sql." Faild! Cause: ".mysql_error($this->connection());
      exit;
    }
    $records=array();
    if($result->num_rows==0){
      return null;
    }
    while($row = $result->fetch_assoc()) {
      $records[]=$row;
    }
    return $records;
  }
  private function connection(){
    return $this->connection;
  }
  private function close(){
    $this->connection->close;
  }
}