Why is the database empty after I insert html tags into the database?

Here is a regular expression. if the submitted data matches this regular expression, use pdo to insert it to the database. this is the regular expression $ reg & #039; ^. {60,600} $ & #039; but for example, if I insert a few casually written html tags and submit them, it will show that the inserted database has a piece of data but this piece of data... here is a regular expression. if the submitted data matches this regular expression, it will be inserted to the database using pdo.
This is the regular expression $ reg = '/^. {60,600} $/'. However, for example, I inserted several html tags that I wrote casually.
After submission, it is displayed that a piece of data is added to the inserted database, but the data is empty. why?

If I insert some characters or something, for example, all of the following will show why html tags cannot be inserted. I didn't filter html tags, so there is only one regular expression. is it automatically filtered by pdo?

/;'\,.":! @ # $ % ^ &*

Reply content:

Here is a regular expression. if the submitted data matches this regular expression, it will be inserted to the database using pdo.
This is the regular expression $ reg = '/^. {60,600} $/'. However, for example, I inserted several html tags that I wrote casually.
After submission, it is displayed that a piece of data is added to the inserted database, but the data is empty. why?

If I insert some characters or something, for example, all of the following will show why html tags cannot be inserted. I didn't filter html tags, so there is only one regular expression. is it automatically filtered by pdo?

/;'\,.":! @ # $ % ^ &*

The first regular expression contains 60 to 600 characters. your HTML section contains only 37 characters, which cannot be matched.