PHP7 Return Type Declarations

php5-return-type.php

<?php
/**
 * Return type in PHP5.
 * 
 * @copyright 2016 SqueezyWeb
 * @author Mattia Migliorini <[email protected]>
 */

/**
 * Get User instance.
 */
function getUser() {
  // Let's return something else...
  return array();
}

var_dump(getUser());
// Output:
// array(0) {
// }

php7-return-type-declaration-interface.php

<?php
/**
 * PHP7 Return Type Declarations with interfaces.
 * 
 * @copyright 2016 SqueezyWeb
 * @author Mattia Migliorini <[email protected]>
 */

/**
 * User class.
 */
class User {
  
}

/**
 * User factory interface.
 */
interface UserFactoryContract {
  /**
   * Generate a new User object.
   * 
   * Uses Return Type Declaration to establish a strict contract.
   * 
   * @return User
   */
  public static function generate() : User;
}

/**
 * User Factory.
 */
class UserFactory implements UserFactoryContract {
  /**
   * What if we don't declare the return type in the implementation?
   */
  public static function generate() {
    // This method will raise the following fatal error at compile time:
    // PHP Fatal error:  Declaration of UserFactory::generate() must be compatible with UserFactoryContract::generate(): User
  }
  
  /**
   * Let's do it right...or maybe not!
   */
  public static function generate() : User {
    return [];
    // Returns a PHP warning at runtime:
    // PHP Warning:  Uncaught TypeError: Return value of UserFactory::getUserWrong() must be an instance of User
  }
  
  /**
   * This time it's right!
   */
  public static function generate() : User {
    return new User;
  }
}

php7-return-type-declaration.php

<?php
/**
 * Return type declaration in PHP7.
 * 
 * @copyright 2016 SqueezyWeb
 * @author Mattia Migliorini <[email protected]>
 */
 
/**
 * User class.
 */
class User {
  
}

/**
 * Get User without return type declaration.
 */
function maybeGetUser() {
  return [];
}

var_dump(maybeGetUser());
// Output:
// array(0) {
// }
// And we're ok with this, we can still do it.

/**
 * Get user with return type declaration and wrong return type.
 */
function getUserWrong() : User {
  return [];
}

getUserWrong();
// Result:
// PHP Warning:  Uncaught TypeError: Return value of getUserWrong() must be an instance of User, array returned

/**
 * Get User with return type declaration.
 * 
 * This time it's ok!
 */
function getUser() : User {
  return new User;
}

var_dump(getUser());
// Output:
// object(User)#1 (0) {
// }