PHP extending class properties

Question

I have two classes in a PHP application, B extending A for example. Class A has a function which returns some of its other properties in the form of an array of SQL insert queries eg

Class A {
$property_a;
$property_b;
$property_c;
$property_d;

function queries() {
$queries = array();
$queries[] = "INSERT INTO xxx VALUES " . $this->property_a . ", " . $this->property_b";
$queries[] = "INSERT INTO yyy VALUES " . $this->property_b . ", " . $this->property_d";
}
}

I would like class B to have a similar (identical) function which does the same thing for class B's properties, whilst still maintaining the values from class A. The idea being that each query will be passed through a final function all at the same time ie:

$mysqli->query("START TRANSACTION");
foreach($queries as $query) {
if(!$mysqli($query)) {
$mysqli->rollback();
}
}

IF all OK $mysqli->commit();

What would be the simplest way to achieve this? Any advice and ideas appreicated. Thanks!

Answer 1

Within B::queries() you can call the parent's implementation of that method and append your data to the array a::queries() returns.

class B extends A {
  protected $property_e=5;
  public function queries() {
    $queries = parent::queries();
    // In a real application property_e needs to be sanitized/escaped
    // before being mixed into the sql statement.
    $queries[] = "INSERT INTO zzz VALUES " . $this->property_e;
    return $queries;
  }
}
$b = new B;
foreach( $b->queries() as $q ) {
  echo $q, "\n";
}

But you might (also) want to look into an ORM library like e.g. doctrine.

Answer 2

Use a getter function to grab the properties in queries(). In each class you can then control what values the queries function is using.

Answer 3

You can't really carry over stuff from one instance to another without initializing the newer class with the other instance's information. So you can extend A to change B's query function contents, then initialize B with an A instance:

class A {
    protected $propa = "";
    protected $propb = "";
    //etc

function query { /*...*/ }
}

class B extends A {
    function __construct( A $classA )
    {
        $this->propa = $classA->propa;
        // etc
    }
    function query()
    {
        //B-type queries
    }
}

$A = new A();
// set stuff in a
new B( $A );

If A and B are 100% the same (including query function), just clone A: $a = new A(); $b = clone $a;

Answer 4

so you want to use the properties in class A and class B? you can do this by using parent. in class B:

function queries(){
  $queries = array()
   //stuff to get queries

  return array_merge($queries,parent::queries());
}