delegatr

PHP 5.5+ delegate system

Installation

Install via cli using composer:

php composer.phar require jgswift/delegatr:0.1.*

Install via composer.json using composer:

{
    "require": {
        "jgswift/delegatr": "0.1.*"
    }
}

Dependency

• php 5.5+
• jgswift/FunctionParser - forked from jeremeamia/FunctionParser
• adlawson/veval.php - eval fallback using virtual file system

Usage

Built-in Lambda (with Serializable)

One of the cumbersome aspects of closures in php is the need to explicitly define the context variables with the "use" statement. Delegates can make that process less painful by allowing you to specify an associative array to dynamically define context.

$x = 10;
$y = 2;

$lambda = new delegatr\Lambda(function() {
    return $x + $y;
}, get_defined_vars());

var_dump($lambda()); // 12

get_defined_vars returns a (non-referenced) list of variables defined in the same scope get_defined_vars is called. Thus $x and $y are dynamically added the the closure's "use" statement and inserted into the closure scope at run-time.

Writing Custom Serializable Closures (using trait)

Delegatr doesn't just wrap closures in an object, it uses eval to enable the serialization of closures - something native php can not do.

The following class uses the Serializable delegate to accomplish this.

class MyDelegate {
    use delegatr\Serializable;
}

$delegate = new MyDelegate(function() {
    return 'foo';
});

$serial_string = serialize($delegate);

$delegate2 = unserialize($serial_string)

var_dump($delegate2()); // returns 'foo';

Using the above trait prevents delegatr from imposing on your domain but if that isn't a concern just instantiate or inherit the Lambda class as shown below.

$delegate = new delegatr\Lambda(function() {
    return 'foo';
});

class MyLambda extends delegatr\Lambda {
    /* ... */
}

Simple delegate (without serialization)

A simpler implementation is also available without \Serializable included

class MyDelegate {
    use delegatr\Delegate;
}

$delegate = new MyDelegate(function() {
    return 'foo';
});

var_dump($delegate()); // returns 'foo';

Eval Fallback & Vulnerability

The eval function is heavily relied on in this package.
If you are not comfortable with eval or do not understand the security risks, I do not suggest you use this package.

However, eval itself is not required for this package.
Delegatr uses adlawson/veval.php to compile scripts at run-time even in environments where eval is disabled. Bypassing eval in this way doesn't reduce the risk of code injection.