Writing and reading from / to MySQL, Yandex.Maps script?

Question

Yandex

Good afternoon, we are making an interactive map where visitors can add tags themselves.
Already broke their heads, but, nevertheless, they found a solution in PHP + MySQL.
The map is displayed, tags are added, but when the page is refreshed, everything disappears, neither writing nor reading from the database occurs.
Help me please ? I have no idea where else to turn.
Attached is the archive with the files.
Archive with files.

Answer 1

addmetki-cat.php:
There is no file in the archive.
Interested in other options?

Answer 2

I would strongly recommend changing the type for the latitude and longitude fields. Set it to decimal. Eight digits after the decimal point should be enough.