PHP protects internal files from being accessed

If it is a php file loaded by internal require and is not displayed in the URL, how can it be better protected?

First write

<code><span><span>define</span></span>(<span>'IN_SYS'</span>, <span>true</span>);</code>

in the entry file and then write a sentence at the beginning of other internal files

<code><span>if</span>(!<span>defined</span>(<span>'IN_SYS'</span>)) <span>die</span>(<span>'Access Denied!'</span>);</code>

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The above introduces PHP to protect internal files from being accessed, including aspects of the content. I hope it will be helpful to friends who are interested in PHP tutorials.