erebot/callable-wrapper

Callable wrapper for PHP < 5.4.0

1.0.0 2016-07-16 16:21 UTC

Requires

• php: >=5.3.0
• ext-spl: *

Requires (Dev)

• phpunit/phpunit: *
• squizlabs/php_codesniffer: *

GPL-3.0+

• François Poirotte

• callable

README

Warning

This component is now deprecated and is unneeded in newer versions of PHP. Do not use it in new code.

Installation

Download the composer.phar executable or use the installer.

$ curl -sS https://getcomposer.org/installer | php

Create a composer.json that requires Erebot's Callable component.

{
    "require": {
        "erebot/callable-wrapper": "dev-master"
    }
}

Run Composer.

$ php composer.phar install

Usage

To use the wrapper, first include composer's autoloader and call Erebot\\CallableWrapper::initialize(), this will make sure everything is set up properly.

Now, use Erebot\\CallableWrapper::wrap() every time you want to execute some callable code while using the callable typehint.

<?php
    // Load composer's autoloader
    require_once PROJECT_ROOT . DIRECTORY_SEPARATOR . 'vendor' . DIRECTORY_SEPARATOR . 'autoload.php';

    // Initialize the wrapper
    Erebot\CallableWrapper::initialize();

    // Define a function/method that uses the "callable" typehint
    // as you normally would, even for PHP 5.3.x.
    function invokeCode(callable $code) {
        $result = null;
        $code($result);
        return $result;
    }

    // Wrap some code to make it compatible with the typehint.
    // In this case, we used a closure, but you may use anything
    // that is callable by PHP's standards (eg. a function, a method,
    // an anonymous function or an invokable object would be fine too)
    $wrapped = Erebot\CallableWrapper::wrap(
        function (&$retval) {
            $retval = 42;
        }
    );

    // Outputs "int(42)" because the $result from invokeCode()
    // was by reference to the wrapped closure and modified there.
    var_dump(invokeCode($wrapped));
?>

How it works

This is really a two-part process.

Under the hood, the wrapper's initialize method first checks whether it is running on PHP 5.3.x or not. If it is, then Erebot\\CallableInterface gets aliased as callable in every currently-defined namespace. It also defines an autoloader which is in charge of defining that class on the fly in the current namespace when required. This is necessary for code such as the following where callable is used as a variable rather than directly as a typehint:

<?php
    $baseClass = "callable";
    if ($objClass instanceof $baseClass) {
        // ...
    }
?>

Since the callable typehint is only an alias to an interface, this is why you need to wrap your code using the wrap method provided, to convert your callable code into an object compatible with that interface.

This is where the magic of the wrapper's wrap method comes in. It checks whether the given code is actually callable and then identifies that code's signature (names of its arguments, which ones have default values, which ones are passed by reference etc.) It then creates a new class on the fly that implements the Erebot\\CallableInterface interface by defining an __invoke magic method with that same signature.

To speed things up a little and to avoid using too much memory, the wrap method uses a cache, where only a single class is ever created for the same code signature.

Hence, code which relies on this wrapper works the same way both on PHP 5.3.x and on later versions.

License

Erebot's Callable component is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

Erebot's Callable component is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with Erebot's Callable component. If not, see <http://www.gnu.org/licenses/>.