Best way to do multiple constructors in PHP

Question

Best way to do multiple constructors in PHP

You can't put two __construct functions with unique argument signatures in a PHP class. I'd like to do this

class Student 

{

   protected $id;

   protected $name;

   // etc.



   public function __construct($id){

       $this->id = $id;

      // other members are still uninitialized

   }



   public function __construct($row_from_database){

       $this->id = $row_from_database->id;

       $this->name = $row_from_database->name;

       // etc.

   }

}

What is the best way to do this in PHP?

constructor php

3 years ago by vishaljlf39

3 Answers

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**rahul07** · Answer 1 · 2021-07-29T12:44:10

I'd probably do something like this:



<?php



class Student

{

    public function __construct() {

        // allocate your stuff

    }



    public static function withID( $id ) {

        $instance = new self();

        $instance->loadByID( $id );

        return $instance;

    }



    public static function withRow( array $row ) {

        $instance = new self();

        $instance->fill( $row );

        return $instance;

    }



    protected function loadByID( $id ) {

        // do query

        $row = my_awesome_db_access_stuff( $id );

        $this->fill( $row );

    }



    protected function fill( array $row ) {

        // fill all properties from array

    }

}



?>

Then if i want a Student where i know the ID:



$student = Student::withID( $id );

Or if i have an array of the db row:



$student = Student::withRow( $row );

Technically you're not building multiple constructors, just static helper methods, but you get to avoid a lot of spaghetti code in the constructor this way.

**RoliMishra** · Answer 2 · 2021-08-02T12:19:48

PHP is a dynamic language, so you can't overload methods. You have to check the types of your argument like this:

class Student 

{

   protected $id;

   protected $name;

   // etc.



   public function __construct($idOrRow){

    if(is_int($idOrRow))

    {

        $this->id = $idOrRow;

        // other members are still uninitialized

    }

    else if(is_array($idOrRow))

    {

       $this->id = $idOrRow->id;

       $this->name = $idOrRow->name;

       // etc.  

    }

}

**pankajshivnani123** · Answer 3 · 2021-08-03T12:20:02

public function __construct() {

    $parameters = func_get_args();

    ...

}



$o = new MyClass('One', 'Two', 3);

Now $paramters will be an array with the values 'One', 'Two', 3.

Edit,

I can add that

func_num_args()

will give you the number of parameters to the function.

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Best way to do multiple constructors in PHP

3 Answers

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