..index::

single: Caching; ExpressionLanguage

Caching Expressions UsingParserCaches

Caching Expressions UsingParser Caches

The ExpressionLanguage component already provides a

:method:`Symfony\\Component\\ExpresionLanguage\\ExpressionLanguage::compile`

:method:`Symfony\\Component\\ExpressionLanguage\\ExpressionLanguage::compile`

method to be able to cache the expressions in plain PHP. But internally, the

component also caches the parsed expressions, so duplicated expressions can be

compiled/evaluated quicker.

The Workflow

Both ``evaluate`` and ``compile``needs to do some things beforeit can

Both ``evaluate`` and ``compile``need to do some things beforeeach can

provide the return values. For ``evaluate``, this overhead is even bigger.

Both methods need to tokenize and parse the expression. This is done by the

:method:`Symfony\\Component\\ExpressionLanguage\\ExpressionLanguage::parse`

method. It'll return a:class:`Symfony\\Component\\ExpressionLanguage\\ParsedExpression`.

method. It returns a:class:`Symfony\\Component\\ExpressionLanguage\\ParsedExpression`.

Now, the ``compile`` method just returns the string conversion of this object.

The ``evaluate`` method needs to loop through the "nodes" (pieces of an

expression saved in the ``ParsedExpression``) and evaluate them on the fly.

To save time, the ``ExpressionLanguage`` caches the ``ParsedExpression``, so

To save time, the ``ExpressionLanguage`` caches the ``ParsedExpression`` so

it can skip the tokenize and parse steps with duplicate expressions.

The caching is done by a

:class:`Symfony\\Component\\ExpressionLanguage\\ParserCache\\ParserCacheInterface`