[PHP] Strict error on static call? Solved!

Just a quick post about Strict standard error when we have a class method which would like to behave differently if called statically.
Apparently, and this is a truly old bogus I opened ages ago, the solution was to supress Strict errors (lol, thanks developers) even if in every other programming language, via overload, this kind of situation could be solved in a bit.

How to solve the problem?

While last post I suggested a couple of runtime solutions, this time I suggest to simply avoid the method definition and use a different one with a meaningful name. In this example I created a String class:

class String {

    // choose a recognizable name for protected method
    static  protected   function    _concat(array $arguments){
        return  new self(implode('', $arguments));
    }

    // use magic __callStatic function
    static  public  function    __callStatic($name, array $arguments){
        // check the recognizable name
        switch($name = '_'.$name){
            case    '_concat':
                // return its call
                return  self::$name($arguments);
        }
    }

    protected   $__value__; // save the string somewhere

    // assign initial string, if any
    public  function    __construct($__value__ = ''){
        $this->__value__ = $__value__;
    }

    // use magic __call method
    public  function    __call($name, array $arguments){
        // check the recognizable name
        switch($name = '_'.$name){
            case    '_concat':
                // normalize expected arguments
                array_unshift($arguments, $this->__value__);
                // return its call
                return  self::$name($arguments);
        }
    }

    // this is a String class ... 
    public  function    __toString(){
        return  $this->__value__;
    }

}


// test the alchemy
$str = new String('Hello');
var_dump(
    String::concat('Hello', ' ', 'World', '!') == $str->concat(' ', 'World', '!')
    // true, both are Hello World!
);

As we can see, errors are gone and the code is much easier to maintain. Hope this will help (performances? ... oh, come on!)

PHP or JavaScript implicit Factory method design pattern

Update
Above technique could be used to create an implicit Singleton as well.

class Demo {
    // your unbelievable stuff
}

function Demo($some, $arg){
    static $instance;
    return isset($instance) ? $instance : ($instance = new Demo($some, $arg));
}

Demo(1,2)->doStuff();
Demo(1,2) === Demo(1,2); // true

from Wikipedia
The factory method pattern is an object-oriented design pattern ... More generally, the term factory method is often used to refer to any method whose main purpose is creation of objects.

I have talked about JavaScript possibility different times in my prototypal inheritance documentation, and in other posts of this blog. The summary is that thanks to perfect this behaviour, that for some unknown reason someone would like to modify in JS2, making them ambiguous when you are using a constructor as a function and not, for example, as private method, we can create intelligent constructors that does not require the usage of new keyword - in a Pythonic way:

// JavaScript
function Person(name, age){
    if(this instanceof Person){
        this.name = name;
        this.age  = age;
    } else
        return new Person(name, age);
};
Person.prototype.getInfo = function(){
    return  this.name + " is " + this.age + " years old";
};

// Example
alert(
    Person("Andrea", 30).getInfo() // Andrea is 30 years old
);

var a = Person("Luca", 25),
    b = Person("Fabio", 31);

The main advantage, using this technique, is that we write less code and we are able to concatenate every public method, allowing us to do different stuff in few lines.

alert(
    Person(name, age).transFormToEmployee(company).getInfo()
);

The new keyword

We could use simply constructor when we would like to create an instance and use then directly a public method.

var time = (new Date).getTime();

// same as
var time = new Date().getTime();

// different of
var time = new Date.getTime(); // Date.getTime is not a constructor !!

Above examples show JavaScript new keyword nature, and its priority when we use brackets around, or at the of the constructor - passing, or not, one or more arguments. With implicit factory method purpose, we could simply do stuff like this one:

// just a basic (and wrong) example of implicit factory implementation
Date = function(Date){
    return function(){
        return this instanceof Date ? this : new Date;
    };
}(Date);

var time = Date().getTime();

To be honest, with native or defined constructors, we should put more effort to implement my proposed technique, but the aim of this post is to show how could be possibile to do the same, with PHP.

PHP implicit Factory method

I suppose that if you are an Object Oriented PHP Programmer, you have tried, at least once, to do something like this and without success:

echo new Person("Me", 30)->getInfo();
echo (new Person("Me", 30))->getInfo();

Since in PHP both usage of brackets and syntax are different, the "only" way we have to concatenate public methods is to create a manual factory one:

class Person {

    // ... our stuff ...
    
    static public function create($name, $age){
        return new Person($name, $age);
    }
}

echo Person::create($name, $age)->getInfo();

Above example is a very common one in many OO frameworks or libraries.

Ambiguity

You probably don't know that thanks to some intrinsic PHP language ambiguity, it is possible to create a function with the same name of a class, as is, for example, for constants, but this time without future features problems.

// PHP
class Person {
    function Person($name, $age){
        $this->name = $name;
        $this->age  = $age;
    }
    function getInfo(){
        return  "{$this->name} is {$this->age} years old";
    }
}

// factory method!!!
function Person($name, $age){
    return new Person($name, $age);
}

// Example
echo Person("Andrea", 30)->getInfo(); // Andrea is 30 years old
?>

The PHP interpreter is able to recognize if we are calling the class or the function, simply looking at new keyword.
If we are using them, it will be obviously an instance creation, while if we are not using them, it will be obviously a function call.
The last case is if we do not use brackets, and then it will be the defined constant, if any, or, in a better future, the static public __toString method, if any again.

The __autofactory function

Since this way to code and use classes and functions could be truly interesting, and since we could have one to thousands of classes, it is natural to think how to automatically implement this kind of feature in our project.
The answer is a function, called __autofactory, that will be able to create a file to include, or require, that will contain every defined class as function, using best practices to speed up implicit factory method usage.
The only thing to write before logic code execution, is this piece of code:

// ... application classes inclusions

// before code logic
require '__autofactory.php';
!file_exists($fileName = 'factory.function.php') && __autofactory($fileName);

The first parameter will be the name of the file that will contain informations, while the second one will specify, if present and with a false evaluable data, if function should require them or not.

At this point, you have basis and / or code to use this particular feature for every kind of purpose.

Natural JavaScript private methods

I've never seen this technique yet, but basically it allows us to create private methods, without privileged, and in an way that does not allow subclasses to inherit them ... does it sound interesting? ;)

As we can read in my JavaScript Prototypal Inheritance for Classical Emulation documentation, there is a way to easily create private methods without usage of privileged.

The advantage of this way is, as explained in my doc, is that JavaScript interpreter does not have to create many functions for each declared instance.

Here there is a basic example:

// our constructor
function Person(name, age){
    this.name = name;
    this.age  = age;
};

// prototype assignment
Person.prototype = (function(){

    // we have a scope for private stuff
    // created once and not for every instance
    function toString(){
        return this.name + " is " + this.age;
    };

    // create the prototype and return them
    return {

        // never forget the constructor ...
        constructor:Person,

        // "magic" toString method
        toString:function(){

            // call private toString method
            return toString.call(this);
        }
    };
})();

// example
alert(
    new Person("Andrea", 29)
);   // Andrea is 29

Function toString will be shared by prototype with every created instance for the simple reason that every instance will inherit prototype.toString method and, at the same time, it points to private scope where toString function has been defined.
Is everything ok? Perfect, because we have to comprehend quite perfectly above example to understand what we are going to do right now ( and if you do not understand, read my doc to know more :P )

What we have to do each time is to remember that when we need a private method, with our instance injected scope, we have to write in an unnatural way.

What I mean is that if we usually use the underscore prefix to define our virtually protected methods, why couldn't we use them to define a function for private stuff only?

// our constructor
function Person(name, age){
    this.name = name;
    this.age  = age;
};

// prototype assignment
Person.prototype = (function(){

    // private stuff
    function toString(){
        return this.name + " is " + this.age;
    };

    // prototype
    return {

        constructor:Person,

        toString:function(){

            // call private toString method
            // in a more natural way
            return this._(toString)();
        },

        // define private methods dedicated one
        _:function(callback){

            // instance referer
            var self = this;

            // callback that will be used
            return function(){
                return callback.apply(self, arguments);
            };
        }
    };
})();

// example
alert(
    new Person("Andrea", 29)
);   // Andrea is 29

The difference is basically in this line of code:

// instead of this way
return toString.call(this);

// we have this one
return this._(toString)();

Please do not forget that these methods are private, so there is no way to use them in subclasses, if those are created in an external or different closure, and that is exactly an expected behaviour (these functions are private).
But at the same time, if a subclass call an inherited method that use inside the parent prototype the private underscore, it will work perfectly.

// basic extend function
function extend(B, A){
    function I(){};
    I.prototype = A.prototype;
    B.prototype = new I;
    B.prototype.constructor = B;
    B.prototype.parent = A;
};

// same stuff ...
function Person(name, age){
    this.name = name;
    this.age  = age;
};
Person.prototype = (function(){
    function toString(){
        return this.name + " is " + this.age;
    };
    return {
        constructor:Person,
        toString:function(){
            return this._(toString)();
        },
        _:function(callback){
            var self = this;
            return function(){
                return callback.apply(self, arguments);
            };
        }
    };
})();

// subclass
function Employee(company, name, age){
    this.parent.call(this, name, age);
    this.company = company;
};

extend(Employee, Person);

Employee.prototype.getFullDetails = function(){
    // toString has been inherited from Person
    // and it uses inside the private method
    return this.toString() + " and works in " + this.company;
};

var other = new Employee("Mega Ltd", "Daniele", 26);
alert(
    other.getFullDetails()
);

Finally, what we can do with this method, is to redefine them to allow us to overwrite private functions and/or use them without problems:

// above stuff + subclass
function Employee(company, name, age){
    this.parent.call(this, name, age);
    this.company = company;
};

extend(Employee, Person);

// extend prototype and return them
Employee.prototype = (function(proto){

    function toString(){
        return this.company;
    };

    proto.toString = function(){
        return this.parent.prototype.toString.call(this) + " and works in " + this._(toString)();
    };

    proto._ = function(callback){
        var self = this;
        return function(){
            return callback.apply(self, arguments);
        };
    };

    return proto;
})(Employee.prototype);

alert(new Employee("Mega Ltd", "Daniele", 26));
// Daniele is 26 and works for Mega Ltd

That's it :)

My 5 cents about JavaScript Prototypal Inheritance

Few days ago I read an interesting post about Simple JavaScript Inheritance.
The most hilarious thing is that prototypal inheritance is truly simple, as John wrote, but there are still a lot of developers that do not probably understand perfectly them.

In this link you can find an "all in one" page about JavaScript prototypal inheritcance and classical emulation.

As I wrote at the end of that page, please do not hesitate to correct me if there is something wrong, or please ask me more details if there is something that is not so clear.

Sorry for my not perfect yet English, and have fun with JavaScript.

(happy easter too!)