Proposal: Dump circular references in var_export() using IIFE

When having $a = array(&$a) and calling var_export($a), instead of getting

PHP Warning:  var_export does not handle circular references in php shell code on line 1
array (
  0 => NULL,
)

we could make it return an IIFE like ((function(){$a = array(&$a);return $a;})()) so we can declare that circular reference using a variable without the risk to change variables in the code where the output of var_export() will be used.

首先使用 var_export() 重现循环引用示例，并检查其实现以及现有的循环引用测试。当 var_export() 能够使用所提议的 IIFE 形式表示自引用，且不会出现警告或丢失引用时，即表示完成。