I have problem with PHP Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result

Please can you help me what i need to do?
nonstop i have that error on my server

PHP Warning: mysqli_fetch_array() expects parameter 1 to be mysqli_result, boolean given in /var/www/mydomain.com/public_html/includes/db_mysqli.php on line$n line 85, referer: http://m.facebook.com

Here is db_mysqli.php file

<?php
class Database{
   private $con = false;
  private $conect = "";
   private $result = array();
  private $query = "";
   public function connect(){

     if(!$this->con){
       $this->conect = new mysqli( _host, _user, _pass, _base );
       $this->conect->set_charset("utf8");
          
  if($this->conect->connect_errno > 0){
  array_push($this->result,$this->conect->connect_error);
  return false;
  }else{
  $this->con = true;
  return true;
  }

  }else{ 
  return true;
  }   
   }

  public function close(){
     if($this->con){

       if($this->conect->close()){

         $this->con = false;

         return true;
       }else{
         return false;
       }
     }
  }

   public function query($query){
     $query = $this->conect->query($query);
     return $query;
   }

   public function fetch_array($sql){
     $array = mysqli_fetch_array($sql);
     return $array;
   }  

   private function tableExists($table){

     $tablesInDb = $this->conect->query('SHOW TABLES FROM '._base.' LIKE "'.$table.'"');

  if($tablesInDb){
     if($tablesInDb->num_rows == 1){
  return true;
  }else{
     array_push($this->result,$table." does not exist in this database");
  return false;
  }
  }
  }

   public function num_rows($query)
   {
     return mysqli_num_rows($query);
   }
}
?>

PHP:

 

Query is returning false instead of whatever you wanted it to return. Use error reporting (http://php.net/manual/en/mysqli.error.php) to find out why.