The PropertyAccess Component

The PropertyAccess Component

The PropertyAccess component provides function to read and write from/to an object or array using a simple string notation.

Installation

You can install the component in two different ways:

Then, require the vendor/autoload.php file to enable the autoloading mechanism provided by Composer. Otherwise, your application won't be able to find the classes of this Symfony component.

Usage

The entry point of this component is the PropertyAccess::createPropertyAccessor factory. This factory will create a new instance of the PropertyAccessor class with the default configuration:

use Symfony\Component\PropertyAccess\PropertyAccess;

$accessor = PropertyAccess::createPropertyAccessor();

Reading from Arrays

You can read an array with the PropertyAccessor::getValue method. This is done using the index notation that is used in PHP:

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// ...
$person = array(
    'first_name' => 'Wouter',
);

var_dump($accessor->getValue($person, '[first_name]')); // 'Wouter'
var_dump($accessor->getValue($person, '[age]')); // null

As you can see, the method will return null if the index does not exists.

You can also use multi dimensional arrays:

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// ...
$persons = array(
    array(
        'first_name' => 'Wouter',
    ),
    array(
        'first_name' => 'Ryan',
    )
);

var_dump($accessor->getValue($persons, '[0][first_name]')); // 'Wouter'
var_dump($accessor->getValue($persons, '[1][first_name]')); // 'Ryan'

Reading from Objects

The getValue method is a very robust method, and you can see all of its features when working with objects.

Accessing public Properties

To read from properties, use the "dot" notation:

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// ...
$person = new Person();
$person->firstName = 'Wouter';

var_dump($accessor->getValue($person, 'firstName')); // 'Wouter'

$child = new Person();
$child->firstName = 'Bar';
$person->children = array($child);

var_dump($accessor->getValue($person, 'children[0].firstName')); // 'Bar'

Caution

Accessing public properties is the last option used by PropertyAccessor. It tries to access the value using the below methods first before using the property directly. For example, if you have a public property that has a getter method, it will use the getter.

Using Getters

The getValue method also supports reading using getters. The method will be created using common naming conventions for getters. It camelizes the property name (first_name becomes FirstName) and prefixes it with get. So the actual method becomes getFirstName:

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// ...
class Person
{
    private $firstName = 'Wouter';

    public function getFirstName()
    {
        return $this->firstName;
    }
}

$person = new Person();

var_dump($accessor->getValue($person, 'first_name')); // 'Wouter'

Using Hassers/Issers

And it doesn't even stop there. If there is no getter found, the accessor will look for an isser or hasser. This method is created using the same way as getters, this means that you can do something like this:

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// ...
class Person
{
    private $author = true;
    private $children = array();

    public function isAuthor()
    {
        return $this->author;
    }

    public function hasChildren()
    {
        return 0 !== count($this->children);
    }
}

$person = new Person();

if ($accessor->getValue($person, 'author')) {
    var_dump('He is an author');
}
if ($accessor->getValue($person, 'children')) {
    var_dump('He has children');
}

This will produce: He is an author

Magic __get() Method

The getValue method can also use the magic __get method:

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// ...
class Person
{
    private $children = array(
        'Wouter' => array(...),
    );

    public function __get($id)
    {
        return $this->children[$id];
    }
}

$person = new Person();

var_dump($accessor->getValue($person, 'Wouter')); // array(...)

Magic __call() Method

At last, getValue can use the magic __call method, but you need to enable this feature by using PropertyAccessorBuilder:

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// ...
class Person
{
    private $children = array(
        'wouter' => array(...),
    );

    public function __call($name, $args)
    {
        $property = lcfirst(substr($name, 3));
        if ('get' === substr($name, 0, 3)) {
            return isset($this->children[$property])
                ? $this->children[$property]
                : null;
        } elseif ('set' === substr($name, 0, 3)) {
            $value = 1 == count($args) ? $args[0] : null;
            $this->children[$property] = $value;
        }
    }
}

$person = new Person();

// Enable magic __call
$accessor = PropertyAccess::createPropertyAccessorBuilder()
    ->enableMagicCall()
    ->getPropertyAccessor();

var_dump($accessor->getValue($person, 'wouter')); // array(...)

Caution

The __call feature is disabled by default, you can enable it by calling PropertyAccessorBuilder::enableMagicCall see Enable other Features.

Writing to Arrays

The PropertyAccessor class can do more than just read an array, it can also write to an array. This can be achieved using the PropertyAccessor::setValue method:

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// ...
$person = array();

$accessor->setValue($person, '[first_name]', 'Wouter');

var_dump($accessor->getValue($person, '[first_name]')); // 'Wouter'
// or
// var_dump($person['first_name']); // 'Wouter'

Writing to Objects

The setValue method has the same features as the getValue method. You can use setters, the magic __set method or properties to set values:

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// ...
class Person
{
    public $firstName;
    private $lastName;
    private $children = array();

    public function setLastName($name)
    {
        $this->lastName = $name;
    }

    public function __set($property, $value)
    {
        $this->$property = $value;
    }

    // ...
}

$person = new Person();

$accessor->setValue($person, 'firstName', 'Wouter');
$accessor->setValue($person, 'lastName', 'de Jong');
$accessor->setValue($person, 'children', array(new Person()));

var_dump($person->firstName); // 'Wouter'
var_dump($person->getLastName()); // 'de Jong'
var_dump($person->children); // array(Person());

You can also use __call to set values but you need to enable the feature, see Enable other Features.

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// ...
class Person
{
    private $children = array();

    public function __call($name, $args)
    {
        $property = lcfirst(substr($name, 3));
        if ('get' === substr($name, 0, 3)) {
            return isset($this->children[$property])
                ? $this->children[$property]
                : null;
        } elseif ('set' === substr($name, 0, 3)) {
            $value = 1 == count($args) ? $args[0] : null;
            $this->children[$property] = $value;
        }
    }

}

$person = new Person();

// Enable magic __call
$accessor = PropertyAccess::createPropertyAccessorBuilder()
    ->enableMagicCall()
    ->getPropertyAccessor();

$accessor->setValue($person, 'wouter', array(...));

var_dump($person->getWouter()); // array(...)

Checking Property Paths

When you want to check whether PropertyAccessor::getValue can safely be called without actually calling that method, you can use PropertyAccessor::isReadable instead:

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$person = new Person();

if ($accessor->isReadable($person, 'firstName')) {
    // ...
}

The same is possible for PropertyAccessor::setValue: Call the PropertyAccessor::isWritable method to find out whether a property path can be updated:

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$person = new Person();

if ($accessor->isWritable($person, 'firstName')) {
    // ...
}

Mixing Objects and Arrays

You can also mix objects and arrays:

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// ...
class Person
{
    public $firstName;
    private $children = array();

    public function setChildren($children)
    {
        $this->children = $children;
    }

    public function getChildren()
    {
        return $this->children;
    }
}

$person = new Person();

$accessor->setValue($person, 'children[0]', new Person);
// equal to $person->getChildren()[0] = new Person()

$accessor->setValue($person, 'children[0].firstName', 'Wouter');
// equal to $person->getChildren()[0]->firstName = 'Wouter'

var_dump('Hello '.$accessor->getValue($person, 'children[0].firstName')); // 'Wouter'
// equal to $person->getChildren()[0]->firstName

Enable other Features

The PropertyAccessor can be configured to enable extra features. To do that you could use the PropertyAccessorBuilder:

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// ...
$accessorBuilder = PropertyAccess::createPropertyAccessorBuilder();

// Enable magic __call
$accessorBuilder->enableMagicCall();

// Disable magic __call
$accessorBuilder->disableMagicCall();

// Check if magic __call handling is enabled
$accessorBuilder->isMagicCallEnabled(); // true or false

// At the end get the configured property accessor
$accessor = $accessorBuilder->getPropertyAccessor();

// Or all in one
$accessor = PropertyAccess::createPropertyAccessorBuilder()
    ->enableMagicCall()
    ->getPropertyAccessor();

Or you can pass parameters directly to the constructor (not the recommended way):

// ...
$accessor = new PropertyAccessor(true); // this enables handling of magic __call

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.