Analysis of a bug in the strip_tags function of PHP

The PHP function strip_tags provides the ability to remove HTML and PHP tags from strings. This function attempts to return the given string str to remove null characters, HTML and PHP markup results.

Because strip_tags () cannot actually verify HTML, incomplete or broken tags will cause more data to be deleted.

For example, the following code:

Copy codeThe Code is as follows:
<Div> string </div> string <B> hello </B> <div> string </div>

Use strip_tags ($ str, '<div>') to filter data. We may expect the following results:

Copy codeThe Code is as follows:
<Div> string </div> string <stringhello <div> string </div>

The actual operation result is as follows:

Copy codeThe Code is as follows:
<Div> string </div> string

All of this is because of the red left angle bracket. I checked the PHP document and gave a warning:

Because strip_tags () cannot actually verify HTML, incomplete or broken tags will cause more data to be deleted.

Since code correctness cannot be verified before filtering is executed, the code after the tag-related character "<" or ">" is all suspended!