diff --git a/books/free-programming-books-zh.md b/books/free-programming-books-zh.md
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--- a/books/free-programming-books-zh.md
+++ b/books/free-programming-books-zh.md
@@ -607,7 +607,6 @@
 
 ### PHP
 
-* [深入理解 PHP 内核](http://www.php-internals.com/book/)
 * [CodeIgniter 使用手冊](https://web.archive.org/web/20210624143822/https://codeigniter.org.tw/userguide3/) *(:card_file_box: archived)*
 * [Composer中文文档](http://docs.phpcomposer.com)
 * [Phalcon7中文文档](https://web.archive.org/web/20220330065727/myleftstudio.com/) *(:card_file_box: archived)*