Question

i having problem understanding what is wrong with my inheritance. I just can not call most of the function of the parent. below is the function i am stuck.

class MySQLi_DB  extends mysqli {
    private static $_instance = null;
    private function __construct($db="test",$host="localhost", $user="root", $pass="") 
    {

        parent::__construct($host, $user, $pass, $db);
        if (mysqli_connect_error()) {
            die('Connect Error (' . mysqli_connect_errno() . ') '
                    . mysqli_connect_error());
        }
    }
 static public function getDB()
    {
        if(self::$_instance == null)
        {
            self::$_instance = new MySQLi_DB();
        }
        return self::$_instance;

    }


public function insert($table,$data)
        {
           $sql = $this->getQuery($table,$data);
           print $sql;
        }

        public function getQuery($table, $inserts) 
        {
            $lambda = function($value){
                return $this->real_escape_string($value);
            };

            $values = array_map($lambda,$inserts);
            $keys = array_keys($inserts);

            return 'INSERT INTO `'.$table.'` (`'.implode('`,`', $keys).'`) VALUES (\''.implode('\',\'', $values).'\')';
        }

I am having problem calling real_escape_string() function . i have tried using $this->real_escape_string() but i just have to see this error

Fatal error: Using $this when not in
object context in
D:\wamp\www\Driver\MySQLi_DB.php on
line 49

ok may be that could be limitation of lambda function but i have tried it other way by declaring a callback for array_map that also doesn’t allow me to call real_escape_string.

i am calling the function as below.

require_once 'MySQLi_DB.php';
        $db = MySQLi_DB::getDB();

        $insert_data = array("cmsId"=>444,"pageName"=>"New Insert");
        $db->insert("cms",$insert_data);

Please point out where i am doing wrong and what could be the best way to do it. thanks

Answer 1

You can’t use the $this keyword into a lamba function as the scope of the function does not extend to the object whose method contains the lambda

Try a different approach:

 public function getQuery($table, $inserts) 
 {
      $values = array_map(array($this, 'real_escape_string'),$inserts);
      $keys = array_keys($inserts);

      return sprintf('INSERT INTO %s (`%s`) VALUES ("%s")',
           $table,
           implode('`,`', $keys),
           implode('","', $values)
      );
    }

Addendum

If real_escape_string is not a method of your object but the standard msqli method you should change the line

 $values = array_map(array($this, 'real_escape_string'),$inserts);

to

 $values = array_map(array(self::$_instance, 'real_escape_string'),$inserts);

to call the method real_escape string.

The array array(self::$_instance, 'real_escape_string') is a callback array and it is used when you want to call an object method.

The php manual states

A method of an instantiated object is passed as an array containing an object at index 0 and the method name at index 1

and self::$_instance is the mysqli instance you want to call