Question

I have a feeling that what I am trying to do is impossible as I can’t find anything on it. I have a few classes that extend from another class. Inside of the class that is being extended, I have to call some unique code based on which class is calling it.

This is something of an in-depth project, so I created a testcase that should explain what I am trying to do:

class parent {
    function traverseTable($table) {
        foreach($table->getElementsByTagName('tr') {
            $rowCnt++;
            $this->uniqueSearch($rowCnt);
        }
    }
}

class child1 extends parent {
    function search($input) {
        //parse input, get $table
        $this->traverseTable($table);
    }

    function uniqueSearch($rowCnt) {
         echo 'child1';
        //Do different things
    }
}

class child2 extends parent {
    function search($input) {
        //parse input, get $table
        $this->traverseTable($table);
    }

    function uniqueSearch($rowCnt) {
         echo 'child2';
        //Do different things
    }
}

Basically, I want to be able to call the uniqueSearch() function from inside the loop in Class Parent; but the above syntax does not seem to work. Anybody have any ideas? The real size of the uniqueSearch functions vary from 20-100 lines at this point, but might get bigger.

Answer 1

So, you want to call uniqueSearch polymorphically.

1. Your first problem has nothing to do with this, and is that parent is a reserved word:

   Fatal error: Cannot use ‘parent’ as class name as it is reserved on line 2

   Fix that.

2. Your next problem is a simple syntax error:

   Parse error: syntax error, unexpected ‘{‘ on line 4

   Fix that.

3. Then, you have the issue that there is no $table, and no getElementsByTagName in your testcase. Also foreach ($table->getElementsByTagName('tr')) is not valid PHP.

   Fix that.

4. Your testcase doesn’t call any functions.

   Fix that.

Result:

<?php
class base {
    function traverseTable($table) {
        foreach ($table as $element) {
            $rowCnt++;
            $this->uniqueSearch($rowCnt);
        }
    }
}

class child1 extends base {
    function search($input) {
        //parse input, get $table
        // dummy for now:
        $table = Array(0,1,2,3);
        $this->traverseTable($table);
    }

    function uniqueSearch($rowCnt) {
         echo 'child1';
        //Do different things
    }
}

class child2 extends base {
    function search($input) {
        //parse input, get $table
        // dummy for now:
        $table = Array(0,1,2,3);
        $this->traverseTable($table);
    }

    function uniqueSearch($rowCnt) {
         echo 'child2';
        //Do different things
    }
}

$c1 = new child1;
$c2 = new child2;

$c1->search("");
$c2->search("");
?>

And now it works just fine:

child1child1child1child1child2child2child2child2

This question had nothing to do with polymorphism whatsoever, as it turns out; just silly syntax errors.

Thanks for playing.