Multiple Constructors in PHP

PHP does not allow multiple constructors with different argument signatures in a class. This poses a challenge when different scenarios require distinct initialization processes.

One approach is to define two constructor methods:

class Student {
    public function __construct($id) {
        $this->id = $id;
    }

    public function __construct(array $row_from_database) {
        $this->id = $row_from_database['id'];
        $this->name = $row_from_database['name'];
    }
}

However, this approach violates PHP's constructor syntax rules.

To circumvent this limitation, a common solution is to create static factory methods instead:

class Student {
    public function __construct() {
        // Allocate resources here
    }

    public static function withID($id) {
        $student = new self();
        $student->id = $id;
        return $student;
    }

    public static function withRow(array $row) {
        $student = new self();
        $student->id = $row['id'];
        $student->name = $row['name'];
        return $student;
    }
}

With this technique, initialization is performed through static methods instead of the constructor:

$studentWithID = Student::withID(42);
$studentWithRow = Student::withRow(['id' => 42, 'name' => 'John']);

Static factory methods provide a flexible and maintainable way to address multiple initialization scenarios while adhering to PHP's class design principles.