PHP return types will cast variable types if setup wrong

return-type.php

<?php

/**
 * In PHP if you don't turn on strict types return types will interpret and 
 * cast variable types. For example the integer 123 if returned from a method 
 * with a return type of string will return '123'.  
 *
 * Always turn on strict types in your application.
 *
 * declare(strict_types = 1);
 */

class ReturnType
{
	private $number;

	public function __construct(int $number)
	{
		$this->number = $number;
	}

	public function getNumber(): string
	{
		return $this->number;
	}
}

$number = 123;

// This will output 'string'
var_dump(gettype($number));

$returnType = new ReturnType($number);

$number = $returnType->getNumber();

// This will output 'integer'
var_dump(gettype($number));