Setting and using parameters from parent class - php

Question

Is there any way I can write my code something like this:
<?php
class BaseClass {
public $testvar;
public function __construct ($testvar) {
$this->testvar = $testvar;
}
}
class ChildClass1 extends BaseClass {
}
class ChildClass2 extends BaseClass {
}
$bc = new BaseClass('test1');
$cc1 = new ChildClass1();
$bc->testvar = 'test2';
$cc2 = new ChildClass2();
echo $cc1->testvar; // should echo 'test1'
echo $cc2->testvar; // should echo 'test2'
?>
The reason I am asking is so that I don't have to specify the parameters every time I create a new child class. I want to make it so I only have to specify the parameters once (preferably when creating the base class).
Is this possible?

Answer 1

It's the point of object oriented programming that every instance has it's own parameters.
But sometimes you just want to use a class once for the whole application. Like a database controller or a router. You can then use static properties and methods:
class BaseClass {
public static $testvar;
public function __construct ($testvar) {
self::$testvar = $testvar;
}
}
Note that the value of the static $testvar is the same in all objects. You could work around that with something like this:"
class BaseClass {
public $testvar;
public static $test_var;
public function __construct ($testvar = '') {
if (!empty($testvar)) {
self::$test_var = $testvar;
}
$this->testvar = self::$test_var;
}
}
class ChildClass1 extends BaseClass {
}
class ChildClass2 extends BaseClass {
}
$bc = new BaseClass('test1');
$cc1 = new ChildClass1();
echo $cc1->testvar; // should echo 'test1'
BaseClass::$test_var = 'test2';
$cc2 = new ChildClass2();
echo $cc1->testvar; // **should echo 'test1'**
echo $cc2->testvar; // should echo 'test2'