Interface ExpressionVisitor

The visitor needs to be attached to a Webmozart\Expression\Traversal\ExpressionTraverser. The traverser invokes the visitor for every node of the expression tree.

Namespace: Webmozart\Expression\Traversal
Author: Bernhard Schussek bschussek@gmail.com
Since: 1.0
Located at Traversal/ExpressionVisitor.php

Methods summary
`public Webmozart\Expression\Expression`	# `enterExpression( Webmozart\Expression\Expression $expr )` Called when the traverser enters an expression. Called when the traverser enters an expression. Parameters `$expr` The expression. Returns `Webmozart\Expression\Expression` The modified expression.
`public Webmozart\Expression\Expression\|null`	# `leaveExpression( Webmozart\Expression\Expression $expr )` Called when the traverser leaves an expression. Called when the traverser leaves an expression. Parameters `$expr` The expression. Returns `Webmozart\Expression\Expression`\|null The modified expression or `null` if the expression should be removed from the tree.