Removing from list nodes
-----
<?php $foo; $bar; $baz;
-----
array_splice($stmts, 1, 1, []);
-----
<?php $foo; $baz;
-----
<?php
function foo(
    $a,
    $b,
    $c
) {}
-----
array_pop($stmts[0]->params);
-----
<?php
function foo(
    $a,
    $b
) {}
-----
<?php
function foo(
    $a,
    $b,
    $c
) {}
-----
array_pop($stmts[0]->params);
$stmts[0]->params[] = new Node\Param(new Expr\Variable('x'));
$stmts[0]->params[] = new Node\Param(new Expr\Variable('y'));
/* TODO The insertion here should try to to honor the style */
-----
<?php
function foo(
    $a,
    $b, $x, $y
) {}