Scalar Type Hinting in PHP

php-scalars.php

<?php

// See: http://nikic.github.io/2012/03/06/Scalar-type-hinting-is-harder-than-you-think.html
// And RFC: https://wiki.php.net/rfc/scalar_type_hinting_with_cast
//
// Basically the same implementation as outlined in the RFC but with a concept for scalar
// magic to be added to objects at some point in the future.

class MyObjectWithScalarMagic {

    public function __toInt()
    {
        return 1;
    }
    
    public function __toFloat()
    {
        return 1.4;
    }
    
    public function __toBool()
    {
        return false;
    }
    
    public function __toResource()
    {
        return $this->resource;
    }

    public function __toObject()
    {
        return $this;
    }

    public function __toArray()
    {
        return (array)$this;
    }

    // Already implemented
    public function __toString()
    {
        return $this->name;
    }
    
}

class MyObjectWithoutScalarMagic {

}

$withMagic = new MyObjectWithScalarMagic;
$withoutMagic = new MyObjectWithoutScalarMagic;

function testInt(int $number)
{
    // Always an int
    var_dump($number);
}

function testFloat(float $number)
{
    // Always a float
    var_dump($number);
}

testInt((int) $withMagic); // int(1)
testInt(5); // int(5)
testInt(5.0); // int(5)
testInt("5"); // int(5)
testInt(5.3); // fatal error: int expected, float given
testInt(array()); // fatal error: int expected, array given
testInt("word up"); // fatal error: int expected, array given
testInt($withoutMagic); // fatal error: object could not be converted to integer

testFloat((float) $withMagic); // float(1.4)
testFloat(5); // float(5.0)
testFloat(5.0); // float(5.0)
testFloat("5"); // float(5.0)
testFloat(5.3); // float(5.3)
testFloat(array()); // fatal error: float expected, array given
testFloat("word up"); // fatal error: float expected, string given
testFloat($withoutMagic); // fatal error: object could not be converted to float

// (etc.)

// Also enables the casting functionality you'd expect
var_dump((int) $withMagic); // int(1)
var_dump((float) $withoutMagic); // fatal error: object could not be converted to float