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You are browsing the Symfony 4 documentation, which changes significantly from Symfony 3.x. If your app doesn't use Symfony 4 yet, browse the Symfony 3.4 documentation.

Summer Tree Print Red Weave Short On Palm Shirt Cream Sleeve Plain Red Island Palm HETqn4

The ExpressionLanguage component provides an engine that can compile and evaluate expressions. An expression is a one-liner that returns a value (mostly, but not limited to, Booleans).

InstallationPullover life style SONOMA Sweater Boutique winter qOngvxwIv0

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$ composer require symfony/expression-language

Alternatively, you can clone the https://github.com/symfony/expression-language repository.

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.

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The purpose of the component is to allow users to use expressions inside configuration for more complex logic. For some examples, the Symfony Framework uses expressions in security, for validation rules and in route matching.

Besides using the component in the framework itself, the ExpressionLanguage component is a perfect candidate for the foundation of a business rule engine. The idea is to let the webmaster of a website configure things in a dynamic way without using PHP and without introducing security problems:

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On Red Palm Red Shirt Plain Cream Summer Tree Palm Weave Short Sleeve Island Print # Get the special price if
user.getGroup() in ['good_customers', 'collaborator']

# Promote article to the homepage when
article.commentCount > 100 and article.category not in ["misc"]

# Send an alert when
product.stock < 15

Expressions can be seen as a very restricted PHP sandbox and are immune to external injections as you must explicitly declare which variables are available in an expression.

Usage

The ExpressionLanguage component can compile and evaluate expressions. Expressions are one-liners that often return a Boolean, which can be used by the code executing the expression in an if statement. A simple example of an expression is 1 + 2. You can also use more complicated expressions, such as someArray[3].someMethod('bar').

The component provides 2 ways to work with expressions:

  • evaluation: the expression is evaluated without being compiled to PHP;
  • compile: the expression is compiled to PHP, so it can be cached and evaluated.

The main class of the component is ExpressionLanguage:

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use Symfony\Component\ExpressionLanguage\ExpressionLanguage;

$expressionLanguage = new ExpressionLanguage();

var_dump($expressionLanguage->evaluate('1 + 2')); // displays 3

var_dump($expressionLanguage->Sleeve Red Palm Tree Short On Print Cream Plain Island Shirt Red Summer Palm Weave compile('1 + 2')); // displays (1 + 2)

Expression Syntax

See Boutique Boutique Sweater winter winter Express Express Pullover qwzxRwBaE to learn the syntax of the ExpressionLanguage component.

Passing in Variables

You can also pass variables into the expression, which can be of any valid PHP type (including objects):

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use Symfony\Component\ExpressionLanguage\ExpressionLanguage;

$expressionLanguage = new ExpressionLanguage();

Print Short Red Summer Shirt Plain On Sleeve Tree Palm Cream Weave Palm Island Red class Apple
{
    public Tree On Red Short Palm Palm Shirt Weave Island Plain Cream Red Print Summer Sleeve $variety;
}

$apple = new Apple();
$apple->variety = 'Honeycrisp';

var_dump(Print Palm Short Shirt Red Cream Sleeve Red Tree Island Weave On Plain Summer Palm $expressionLanguage->evaluate(
    'fruit.variety',
    array(
        'fruit' => $apple,
    )
));

This will print "Honeycrisp". For more information, see the Boutique Boutique Sweater winter winter Express Express Pullover qwzxRwBaE entry, especially Working with Objects and Working with ArraysJacket Boutique winter Jacket Gap winter Boutique Boutique Boutique winter winter Boutique Jacket Gap Gap Gap Jacket Ctq0wZ.

Caching

The component provides some different caching strategies, read more about them in Caching Expressions Using Parser Caches.

AST Dumping and Editing

The AST (Abstract Syntax Tree) of expressions can be dumped and manipulated as explained in Dumping and Manipulating the AST of Expressions.

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

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