Question

The following is my simplified code

<?php
  $database = new db();
  $file = new file();
  $input = new input();
  $output = new output();

  $data = "SELECT * FROM table;";
  $input->page($data);

  class db {
        public function queryExecute($var) {
              $var = $this->queryEncode($var);
              $var = $this->querySubmit($var);
        return $var;
        }

        public function queryEncode($var) {
              // Do somthing
        return $var;
        }

        public function querySubmit($var) {
              // Do somthing
        return $var;
        }
  }

The issue is when I add this to the code:

  class input {
        public function page($data) {
              // Do something
              $pageQuery = db::queryExecute($data);
        }
  }

With this, there are two things I have to do. First, I have to hide the errors for the db::queryExecute($data); code if the server is set to strict. And now for the second problem. I can’t seem to use this line of code (which is the only way I have yet found possible for referencing other classes besides using Abstract) if the class that is being referenced is referencing yet another class but this time within it’s own class.

For better explanation, the procedure is as follows:

1. Grab the $data variable and send it to the $input->page() function ( $input->page($data) ).
2. Referencing the db class, the $input->page() function sends the information onto the $database->queryExecute() function by means of the db::queryExecute() format ( db::queryExecute($data) ).
3. But because we are using the ::, when $database->queryExecute() references $database->queryEncode() and $database->querySubmit() using $this-> operator ( $this->queryEncode() and $this->querySubmit() ), $this-> currently belongs to $input-> and not $database->.

So what’s the solution… Reference the other class differently (instead of ::)? Use a $_GLOBAL variable when I define my classes? Use something other than $this->? Configure all of the classes to use ABSTRACT/EXTENDS (or INTERFACE)?

The following error outputted refers to $var = $this->queryEncode($var);:

Fatal error: Call to undefined method input::querySubmit() in C:\[...]\global.php on line 12

Answer 1

Do not make static call to not static function. Pass $db instance to page, or provide global access to the database (via global registry, singleton or other method). But best, pass the dependency – the database instance, to the method.

<?php
  $database = new db();
  $file = new file();
  $input = new input($database);
  $output = new output();

  $data = "SELECT * FROM table;";
  $input->page($data);

  class db {
        public function queryExecute($var) {
              $var = $this->queryEncode($var);
              $var = $this->querySubmit($var);
        return $var;
        }

        public function queryEncode($var) {
              // Do somthing
        return $var;
        }

        public function querySubmit($var) {
              // Do somthing
        return $var;
        }
  }

  class input {
    protected $_database;
    public function __construct($database) {
        $this->_database = $database;
    }
    public function page($data) {
          // Do something
          $pageQuery = $this->_database->queryExecute($data);
    }
  }