Why are $GLOBAL[''] and the keyword global affected by static variables in PHP?

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First time encountering this problem. I'm a little curious, how did the questioner discover this problem?

Let me tell you my understanding.

First we need to clarify the concept of "assignment".

When $a = 1;, it does not mean adding a data whose name is $a and whose value is 1.
When $b = &$a;, it doesn’t mean pointing $b to $a or vice versa.

This process is like this:

<code class="language-php"><span class="x">$a = 1;</span>
</code>

Read the PHP manual, there are many examples
PHP: Variable scope
PHP: Explanation of references
PHP: Pass by reference
PHP: What does a reference do

Variable scope

The scope of a variable is the context in which it is defined (that is, its effective scope). Most of the PHP variables have only a single scope. This single range span also contains Files introduced by include and require. For example:

<code class="language-php"><span class="cp"><?php</span>
<span class="nv">$a</span> <span class="o">=</span> <span class="mi">1</span><span class="p">;</span>
<span class="k">include</span> <span class="s1">'b.inc'</span><span class="p">;</span><span class="cp">?></span><span class="x"></span>
</code>

<code class="language-text">global $a;
时会 新建 一个指向与外部$a同地址的指针

$GLOBALS['a'] = &$static_a;
时会 把外部$a 指针 指向 $static_a的内容，抛弃原先的指向
</code>