使用PDO查询的静态函数错误

Question

I'm learning oophp and I have got a little problem.

After 2 hours of search I need your help :(

My class:

<?php
namespace App;
use \PDO;

class Database {
 private $_pdo = null;
 private static $_connexion = null;

 // + my 4 mysql const

 public function__construct(){
  $this->pdo = new PDO ('mysql:dbname='.const.';host='.const.'', const, const);
}

 public static function getPdo(){
  if(is_null(self::$_connexion)){
   self::$_connexion = new Database();
  }
 }

 public static function select($test, $test2){
  self::getPdo();
  if($test == "*"){
   $req = self::$_pdo->query("SELECT * FROM $test2"); // line 29
  }
 }
}
$test = Database::select('*', 'users');

Error: (line29) Fatal Er: Uncaught Error: Access to undeclared static property: App\Database::$_pdo

I don't understand what I have to do, I've not found any similar issues in my research.

Thanks for help!

Edit (sorry): God I'm idiot... I removed static because I had this : Notice: Accessing static property App\Database::$_pdo as non static in line 15 (new PDO...)

The real error is : (when $_pdo is static):

Call to a member function query() on null in line 29

Answer 1

You are trying to access $_pdo as a static variable even though it is not declared as such.

This is a hack, but it works. You can adapt it to your class

class Test {

    private $_pdo ;
    private static $self ;

    function __construct() {
        self::$self = $this ;
    }

    public static function select() {
        self::$self->_pdo = 'test' ;    
    }
}

$t = new Test() ;
$t::select() ;