PHP OOP Design Pattern

Question

I recently read an article on Wikipedia about Design Pattern

So far I've done this, but it returns Fatal error: Maximum function nesting level of '100' reached, aborting!

Logically I know, it will return nesting error, But, I don't understand how is the best step.

class Main {
    $this->Aa = new Aa;
    $this->Bb = new Bb;
    $this->Cc = new Cc;
    }
class Aa extends Main {
    function blahA() {
        // blah blah
        }
    function testA() {
        $ret[] = $this->blahA(); // Call inside class
        $ret[] = $this->Bb->blahB(); // Call outside class
        $ret[] = $this->Cc->blahC(); // Call outside class
        return $ret;
        }
    }
class Bb extends Main {
    function blahB() {
        // blah blah
        }
    function testB() {
        $ret[] = $this->blahB(); // Call inside class
        $ret[] = $this->Aa->blahA(); // Call outside class
        $ret[] = $this->Cc->blahC(); // Call outside class
        return $ret;
        }
    }
class Cc extends Main {
    function blahC() {
        // blah blah
        }
    function testC() {
        $ret[] = $this->blahC(); // Call inside class
        $ret[] = $this->Aa->blahA(); // Call outside class
        $ret[] = $this->Bb->blahB(); // Call outside class
        return $ret;
        }
    }

Basically i want to manage my classes design, in order the method in Aa class is also reusable in Bb class and vice versa. I curious, how to build the relationship like my classes above, How to extends the class to get above pattern? And what is the name of this pattern? please also give me a link that i can learn from.

Many Thanks,

Answer 1

Consider creating Aa and Bb separately and using Dependency Injection so each class will have a reference to the other. You should make sure the two classes are not too tightly coupled though.

The Gang of Four (GoF) Design patterns book mentioned in the comments is a good one, but the Head First Design Patterns is a bit easier (also very enjoyable) for beginners.

Here is an example. Notice there are better ways to set a property in PHP, I put a setter function just to be explicit. Refer to this question for more info.

class Main {
    $this->Aa = new Aa;
    $this->Bb = new Bb;
    $this->Cc = new Cc;

    // Can use properties instead of setters
    $this->Aa->setB(Bb);
    $this->Aa->setC(Cc);

    $this->Bb->setA(Aa);
    $this->Bb->setC(Cc);

    $this->Bb->setA(Aa);
    $this->Bb->setC(Bb);
    }

class Aa {                // No need to extend Main, right?
    function blahA() {
        // blah blah
        }
    // Dependency injection, Bb is now a member of this class
    // Consider doing this with PHP properties instead
    // Using setter function to be more explicit
    function setB(Bb b) {
        this->Bb = b;
        }
    // Dependency injection, Cc is now a member of this class
    // Consider doing this with PHP properties instead
    // Using setter function to be more explicit
    function setC(Cc c) {
        this->Cc = c;
        }
    function testA() {
        $ret[] = $this->blahA(); // Call inside class
        $ret[] = $this->Bb->blahB(); // Call outside class
        $ret[] = $this->Cc->blahC(); // Call outside class
        return $ret;
        }
    }
// Class Bb ...
// Class Cc ...