Edward Kay wrote:
> Hi Richard,
>
> This is very strange. I can certainly reproduce the problem. Putting a
> var_dump($this) in ClassA's save method shows that PHP sees $this as an
> instance of ClassB - when it should be of ClassA.
what *you* think it should be and what php's developers decided it should be
about 3+ years ago obviously differ.
if you have an instance of ClassB it is exactly that - refering to $this
in the parent class definition won't magically make the class of the instance change.
$this is plain this and not something else.
here is a code snippet to chew on - hope it gives you a lightbulb moment:
class A {
function test() { self::test2(); }
function test2() { echo "TEST: ",__CLASS__,"\n"; }
}
class B extends A {
function test2() { echo "TEST: ",__CLASS__,"\n"; }
}
$b = new B; $b->test(); $b->test2();
>
> I'm afraid it's stumped me too! Does anyone else have any thoughts?
RTM - especially the php5 OO section(s)
>
> Edward
>
>
>> Hi,
>>
>> I came across this problem and I was wondering if someone might be able
>> to explain to my why it is happening. I put together a short example to
>> illustrate the problem that I am having.
>>
>> Basically I have one class that performs a certain task. I then have a
>> second class which extends the first class and performs some tasks in
>> addition to the first class. Even though ClassA should know nothing
>> about ClassB since ClassA is the parent, ClassA actually calls ClassB's
>> exist method when it should be calling it's own.
>>
>> I know that description is really wordy and probably confusing which is
>> why I provided below the example code that illustrates the problem.
>>
>> Doesn't this break the idea of inheritance? I can get it to work if I
>> change ClassB::exists to some other name such as ClassB::exists2.
>>
>> If anyone can enlighten me as to why this problem is occurring or
>> suggest a fix I would really appreciate it. Thank you.
>>
>>
>>
>> expected output
>> ---------------
>> ClassB - save
>> ClassA - save
>> ClassA - exists
>> ClassA - update
>>
>>
>>
>> actual output
>> -------------
>> ClassB - save
>> ClassA - save
>>
>>
>> Warning: Missing argument 2 for ClassB::exists(), called in
>> /website/overridetest.php on line 6 and defined in
>> /website/overridetest.php on line 33
>>
>> ClassB - exists
>> ClassA - update
>>
>>
>>
>> overridetest.php
>> ----------------
>> <?php
>> class ClassA {
>> public function save($value) {
>> echo "ClassA - save\n";
>>
>> if ($this->exists($value))
>> $this->update($value);
>> else
>> $this->insert($value);
>> }
>>
>> protected function insert($value) {
>> echo "ClassA - insert\n";
>> }
>>
>> protected function update($value) {
>> echo "ClassA - update\n";
>> }
>>
>> public function exists($value) {
>> echo "ClassA - exists\n";
>> return true;
>> }
>> }
>>
>> class ClassB extends ClassA {
>> public function save($value, $classAValue) {
>> echo "ClassB - save\n";
>> parent::save($classAValue);
>> // do some additional work...
>> }
>>
>> public function exists($value, $classAValue) {
>> // does a different search than ClassA
>> echo "ClassB - exists\n";
>> return true;
>> }
>> }
>>
>> $c = new ClassB();
>> $c->save('test', 'test2');
>> ?>
>>
>> --
>> Richard Morris
>> HDD Broker, Inc.
>>
>> Toll-Free: +1 866 960-3331
>> International: +1 250 474-6022
>> Fax: +1 250 474-6099
>> E-Mail: richard@xxxxxxxxxxxxx
>> Web Site: www.hddbroker.com
>>
>> --
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>>
>>
>>
>
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