Closures
-----
<?php
function($a) { $a; };
function($a) use($b) {};
function() use($a, &$b) {};
function &($a) {};
static function() {};
-----
array(
    0: Expr_Closure(
        static: false
        byRef: false
        params: array(
            0: Param(
                name: a
                default: null
                type: null
                byRef: false
            )
        )
        uses: array(
        )
        stmts: array(
            0: Expr_Variable(
                name: a
            )
        )
    )
    1: Expr_Closure(
        static: false
        byRef: false
        params: array(
            0: Param(
                name: a
                default: null
                type: null
                byRef: false
            )
        )
        uses: array(
            0: Expr_ClosureUse(
                var: b
                byRef: false
            )
        )
        stmts: array(
        )
    )
    2: Expr_Closure(
        static: false
        byRef: false
        params: array(
        )
        uses: array(
            0: Expr_ClosureUse(
                var: a
                byRef: false
            )
            1: Expr_ClosureUse(
                var: b
                byRef: true
            )
        )
        stmts: array(
        )
    )
    3: Expr_Closure(
        static: false
        byRef: true
        params: array(
            0: Param(
                name: a
                default: null
                type: null
                byRef: false
            )
        )
        uses: array(
        )
        stmts: array(
        )
    )
    4: Expr_Closure(
        static: true
        byRef: false
        params: array(
        )
        uses: array(
        )
        stmts: array(
        )
    )
)