php+javascript help!! error

hello,
i have started learning to code just for a year now,
i have a small university project, it’s about localizing some landmarks that are in my city, on google map. i wanted to display markers and each marker has to have his own discription.
i have made the code and i have completed my data-base on Mysql.
i have linked the map to my database but i kept getting an error i couldn’t find out the solution, please i really need your help guys.
you can see all the ffiles i have just done untill now in this link:
https://drive.google.com/drive/folde…UaS4It6MrELm8q

thank you very much guys i hope you can help me please