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Type casting 

 
/**
 * Type casting means converting a variable from one type to another. 
 * The name of the type is written in parentheses.
 */

$arr = ["a" => 1, "b" => 2];
$obj = (object) $arr; // Look here

echo $obj->b; // 2

Type hinting 

 
/**
 * Type hinting (or type declarations) is used to specify the expected type.
 */

declare(strict_types=1);

function add(int $a, int $b): int
{
    return $a + $b;
}

try {
    echo add (1, "2");
} catch (TypeError $e) {
    echo $e->getMessage();  
}

/**
 * add(): Argument #2 ($b) must be of type int, string given
 */

Union types 

 
/**
 * Prior to PHP 8.0 you could only declare a single type for 
 * properties, parameters, and return types.
 * 
 * A union type is a collection of different datatypes in the same memory location.
 * With PHP 8.2 you can use union type in class property declaration.
 * 
 * To separate each datatype use pipe |
 * The ?string is equivalent with string|null
 */

class Test
{
    private  int|float $value = 10;  // Look Here
    private ?string $name;

    public function set(int|float $n, ?string $str): void
    {
        $this->value = $n;
        $this->name = $str;
    }

    public function getValue(): int|float
    {
        return $this->value;
    }

    public function getName(): ?string
    {
        return $this->name;
    }
}

$a = new Test();
$b = new Test();

$a->set(10, "one");
$b->set(5.5, NULL);

echo $a->getValue() . " " . $a->getName() . PHP_EOL; // 10 one
echo $b->getValue() . " " . $b->getName() . PHP_EOL; // 5.5

Object type 

 
/**
 * The default object in PHP is of stdClass type.
 * The stdClass type has no properties, methods or parent.
 */

$A = (object) array();  // OR
$A = new stdClass();

$A->x = 3;
$A->y = 4;

print_r($A);

/**
 * stdClass Object ([x] => 3, [y] => 4)
 */






Questions and answers:
Clink on Option to Answer




1. How do you type cast a variable to integer?

  • a) $a = (int) $a;
  • b) $a = (int $a);

2. Can you use union types in php?

  • a) no
  • b) yes, starting with PHP 8.2

3. Which one is a union type declaration?

  • a) int|float $x = 10;
  • b) int $x = 20;

4. What is a union type?

  • a) A collection of different datatypes in the same memory location
  • b) An if/else condition

5. What ?string is equivalent to?

  • a) string|null
  • b) not a string

6. Is there a difference between type casting and hinting?

  • a) yes, hinting is about what type you expect
  • b) yes, casting is about php automatic type conversion


References: