The PropertyAccess Component

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The PropertyAccess Component

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

Installation

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$ composer require symfony/property-access

Note

If you install this component outside of a Symfony application, you must require the vendor/autoload.php file in your code to enable the class autoloading mechanism provided by Composer. Read this article for more details.

Usage

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

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use Symfony\Component\PropertyAccess\PropertyAccess;

$propertyAccessor = PropertyAccess::createPropertyAccessor();

Reading from Arrays

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

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// ...
$person = [
    'first_name' => 'Wouter',
];

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

As you can see, the method will return null if the index does not exist. But you can change this behavior with the enableExceptionOnInvalidIndex() method:

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// ...
$propertyAccessor = PropertyAccess::createPropertyAccessorBuilder()
    ->enableExceptionOnInvalidIndex()
    ->getPropertyAccessor();

$person = [
    'first_name' => 'Wouter',
];

// instead of returning null, the code now throws an exception of type
// Symfony\Component\PropertyAccess\Exception\NoSuchIndexException
$value = $propertyAccessor->getValue($person, '[age]');

You can also use multi dimensional arrays:

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// ...
$persons = [
    [
        'first_name' => 'Wouter',
    ],
    [
        'first_name' => 'Ryan',
    ],
];

var_dump($propertyAccessor->getValue($persons, '[0][first_name]')); // 'Wouter'
var_dump($propertyAccessor->getValue($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($propertyAccessor->getValue($person, 'firstName')); // 'Wouter'

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

var_dump($propertyAccessor->getValue($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 transforms the property name to camelCase (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($propertyAccessor->getValue($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 = [];

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

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

$person = new Person();

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

This will produce: This person is an author

Accessing a non Existing Property Path

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The disableExceptionOnInvalidPropertyPath() method was introduced in Symfony 4.3.

By default a NoSuchPropertyException is thrown if the property path passed to getValue() does not exist. You can change this behavior using the disableExceptionOnInvalidPropertyPath() method:

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// ...
class Person
{
    public $name;
}

$person = new Person();

$propertyAccessor = PropertyAccess::createPropertyAccessorBuilder()
    ->disableExceptionOnInvalidPropertyPath()
    ->getPropertyAccessor();

// instead of throwing an exception the following code returns null
$value = $propertyAccessor->getValue($person, 'birthday');

Magic __get() Method

The getValue() method can also use the magic __get() method:

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// ...
class Person
{
    private $children = [
        'Wouter' => [...],
    ];

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

$person = new Person();

var_dump($propertyAccessor->getValue($person, 'Wouter')); // [...]

Magic __call() Method

Lastly, 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 = [
        'wouter' => [...],
    ];

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

$person = new Person();

// enables PHP __call() magic method
$propertyAccessor = PropertyAccess::createPropertyAccessorBuilder()
    ->enableMagicCall()
    ->getPropertyAccessor();

var_dump($propertyAccessor->getValue($person, 'wouter')); // [...]

Caution

The __call() feature is disabled by default, you can enable it by calling 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 setValue() method:

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// ...
$person = [];

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

var_dump($propertyAccessor->getValue($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 = [];

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

    public function getLastName()
    {
        return $this->lastName;
    }

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

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

$person = new Person();

$propertyAccessor->setValue($person, 'firstName', 'Wouter');
$propertyAccessor->setValue($person, 'lastName', 'de Jong'); // setLastName is called
$propertyAccessor->setValue($person, 'children', [new Person()]); // __set is called

var_dump($person->firstName); // 'Wouter'
var_dump($person->getLastName()); // 'de Jong'
var_dump($person->getChildren()); // [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 = [];

    public function __call($name, $args)
    {
        $property = lcfirst(substr($name, 3));
        if ('get' === substr($name, 0, 3)) {
            return $this->children[$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
$propertyAccessor = PropertyAccess::createPropertyAccessorBuilder()
    ->enableMagicCall()
    ->getPropertyAccessor();

$propertyAccessor->setValue($person, 'wouter', [...]);

var_dump($person->getWouter()); // [...]

Writing to Array Properties

The PropertyAccessor class allows to update the content of arrays stored in properties through adder and remover methods:

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// ...
class Person
{
    /**
     * @var string[]
     */
    private $children = [];

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

    public function addChild(string $name): void
    {
        $this->children[$name] = $name;
    }

    public function removeChild(string $name): void
    {
        unset($this->children[$name]);
    }
}

$person = new Person();
$propertyAccessor->setValue($person, 'children', ['kevin', 'wouter']);

var_dump($person->getChildren()); // ['kevin', 'wouter']

The PropertyAccess component checks for methods called add<SingularOfThePropertyName>() and remove<SingularOfThePropertyName>(). Both methods must be defined. For instance, in the previous example, the component looks for the addChild() and removeChild() methods to access the children property. The Inflector component is used to find the singular of a property name.

If available, adder and remover methods have priority over a setter method.

Checking Property Paths

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

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$person = new Person();

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

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

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$person = new Person();

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

Mixing Objects and Arrays

You can also mix objects and arrays:

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// ...
class Person
{
    public $firstName;
    private $children = [];

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

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

$person = new Person();

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

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

var_dump('Hello '.$propertyAccessor->getValue($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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// ...
$propertyAccessorBuilder = PropertyAccess::createPropertyAccessorBuilder();

// enables magic __call
$propertyAccessorBuilder->enableMagicCall();

// disables magic __call
$propertyAccessorBuilder->disableMagicCall();

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

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

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

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

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// ...
$propertyAccessor = 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.
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