Accessing private/protected properties of an object in anonymous function in PHP

Question

I'm trying to dump elements of an object's private property through an anonymous function - of course I could achieve this in any number of other ways, but this highlights a PHP conundrum I can't solve off the top of my head, short of $foo = $this and using $foo - but THAT won't give me the private stuff, so... suggestions ?

Sample code:

class MyClass { private $payload = Array( 'a' => 'A element', 'b' => 'B element'); static $csvOrder = Array('b','a'); public function toCSV(){ $values = array_map( function($name) use ($this) { return $this->payload[$name]; }, self::$csvOrder ); return implode(',',$values); } } $mc = new MyClass(); print $mc->toCSV();

Dup of "Accessing private variables from within a closure", but NikiC's answer works for accessing non-public methods as well as non-public properties, so not voting for closure. — outis
– outis, Commented Feb 13, 2012 at 12:24

Jon · Accepted Answer · 2011-06-17 13:52:36Z

I believe there is absolutely no way to do directly what you propose.

However, you can work around it either by making the anonymous method a class method (this is not what you asked for, but it could be a practical solution) or pulling everything you need out of $this explicitly and passing the extracted values into the function:

class MyClass { private $payload = Array( 'a' => 'A element', 'b' => 'B element'); static $csvOrder = Array('b','a'); public function toCSV(){ $payload = $this->payload; $values = array_map( function($name) use ($payload) { return $payload[$name]; }, self::$csvOrder ); return implode(',',$values); } }

Indeed - your code reflects what I ended up doing in this particular case. Oh well, it's an interesting problem in general - was hoping there was a way to address the issue I was simply unaware of. Thanks for the answer :)
+1 I posted an answer with this before I realized that you already said it. The simplest solution is often the best.

NikiC · Accepted Answer · 2011-06-17 13:57:32Z

You can hack around the limitation by creating a wrapper that utilizes Reflection to allow you to access all properties and methods. You can use it like this then:

$self = new FullAccessWrapper($this); function () use ($self) { /* ... */ }

Here a sample implementation of the wrapper, taken from here:

class FullAccessWrapper { protected $_self; protected $_refl; public function __construct($self) { $this->_self = $self; $this->_refl = new ReflectionObject($self); } public function __call($method, $args) { $mrefl = $this->_refl->getMethod($method); $mrefl->setAccessible(true); return $mrefl->invokeArgs($this->_self, $args); } public function __set($name, $value) { $prefl = $this->_refl->getProperty($name); $prefl->setAccessible(true); $prefl->setValue($this->_self, $value); } public function __get($name) { $prefl = $this->_refl->getProperty($name); $prefl->setAccessible(true); return $prefl->getValue($this->_self); } public function __isset($name) { $value = $this->__get($name); return isset($value); } }

Obviously the above implementation doesn't cover all aspects (e.g. it can't use magic properties and methods).

Interestingly evil :) Of course probably not what I'd do for production, but it does solve the problem - thanks

Shay Ben-Moshe · Accepted Answer · 2011-06-17 13:54:17Z

As you said yourself, it is private and therefore in accessible.

You can:

Pass $this->payload as a parameter to the anonymous function.
Create a method in the class and use it instead.

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Accessing private/protected properties of an object in anonymous function in PHP

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