我在wordpress中开发了一个网站。但是现在我面临一个错误：
require(public_html/mywebsite/wp-includes/post.php):failed to open stream: permission denied in public_html/mywebsite/wp-settings.php on line 142
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Fatal error: require(): Failed opening required '/public_html/mywebsite/wp-includes/post.php'(include_path='.:/opt/apt/php55/usr/share/pear:/opt/alt/php55/usr/share/php') in /public_html/indus/wp-settings.php on line 142
为了解决这个问题，我更改了post.php文件的权限。而且有效。但是第二天，当我试图打开它时，我又遇到了同样的问题。
如何解决呢？