andreas andreas - 5 months ago 68
PHP Question

How to use mysqli::fetch_object()?

How do people usually turn mysqli results into objects?

I cannot find any examples with fetch_object() when using custom classes. Assume the following setup

class Test1 {
function __construct(array $data) { ... }
}

class Test2 {
function __construct(array $data) { ... }
}


Assume that I have multiple classes with the same constructors, how can I dynamically instantiate these classes?

I would imagine something like this:

function customQuery($query, $class) {

// Get some data by mysqli query, assume we get the data as $result object
...

// Now I would like to store the data in an array with instances of $class
$array = array();
while ($obj = $result->fetch_object($class, ???) {
$array[] = $obj;
}

// Return the array with instances of $class
return $array;

}


What do I use as arguments there for my question marks? I only know that both class constructors of Test1 and Test2 want an associative array as input (probably not the same length!).

In the end I simply want to do something like

$arr1 = customQuery('SELECT id, product FROM test1 LIMIT 10', 'Test1');
$arr2 = customQuery('SELECT id, name, address FROM test2 LIMIT 10', 'Test2');


Of course I would appreciate your input if you have better ideas to achieve my goal.

Answer

Take a look at "fetch_object'

You have a argument $class_name

From the docs: The name of the class to instantiate, set the properties of and return. If not specified, a stdClass object is returned.

It will automaticly create an instance of the given class and it will set the properties. so no need to pass an array http://www.php.net/manual/en/mysqli-result.fetch-object.php

A bit more explanation,

The fetch_object just fills the private properties etc (PHP Magic... i don't like it).

If your object has required parameters in the constructor but you want to fetch it from the database the fetch_object lets you define arguments for the constructor so it can be constructed instead of throwing warnings/errors.

class Test {
   private $title;
   public function __construct($required) { 

   }
}

$mysql->fetch_object('Test'); //will trigger errors/warnings
$mysql->fetch_object('Test', array(null)); //won't 

What you could do is simpel fetch an array and construct the object

function query($query, $class) {
   $data = $query->fetch_assoc();
   $instance = new $class($data);
   return $instance;
}