Language basics

by Gisle Hannemyr

This chapter ....

Introduction
Final word

Introduction

[TBA]

Constants

PHP provide ways to define constants: Either using the const keyword or the define() function:

const FOO = 'foo';
define('FOO', 'foo');

The difference between those two ways is that const defines constants at compile time, whereas define() defines them at run time.

This means that some constructs that are illegal with const can be used with define(). For example, making the definition conditional is only legal with define().

if (…) {
  const FOO = 'foo';     // ILLEGAL
}
else {
  define('FOO', 'foo');  // OK
}

If you try to assign a value to const that cannot be assigned until runtime, you get a WSOD (but no error is logged).

const FOO = t('bar');    // WSOD
define('FOO', t('bar')); // OK

Constant arrays using define() was introduced in PHP 7.0 (older versions allowed this with const, bit since PHP 7.0, both can be arrays:

const FOO = [1, 2, 3];
define('FOO', [1, 2, 3]);

The keyword const can be used within a class or interface to define a class constant or interface constant. The define() function cannot be used for this purpose:

class Foobar {
  const FOO = 'bar; // OK
}


class Foobar {
  define('FOO', 'bar'); // INVALID
}

Recent changes to PHP

Backwards incompatible changes

count()

In PHP prior to 7.2, the function count() returned 0 if it was given an argument that was not countable (e.g. NULL, integer, string).

A new function is_countable() was introduced in PHP 7.3, and you can do this to emulate the legacy behaviour.

/*
 * Helper function to emulate count() prior to PHP 7.2.
 */
private function _Count($arg) {
  return is_countable($arg) ? count($arg) : 0;
}

https://www.drupal.org/forum/support/module-development-and-code-questions/2021-03-11/help-figuring-out-undefined-function

New constructs in PHP 7

The short array syntax was introduced in PHP 5.4.

The spaceship (<=>) operator comes from Perl, Ruby and Groovy. It offers a combined comparison:

 0 if $a == $b
-1 if $a <  $b
 1 if $a >  $b

Source: wiki.php.net.

The null coalescing operator (??) comes from C# and can be used to avoid isset() to check if a variable exists:

$username = isset($_GET['user']) ? $_GET['user'] : 'nobody'; // old way
$username = $_GET['user'] ?? 'nobody';  // new way

PHP 7.x allows return type declarations, further enhanced in 7.1 by making them (and parameters) nullable. This is very much like C#, as is the types of return typing like this:

function arraysSum(array ...$arrays): array

Strict type enforcement (from PHP 7.1). Just put this line at the top of the page:

declare(strict_types=1);

Final word