Write the necessary code $($HTML$,$ JavaScript, PHP$,$ SQL$)$ to develop a calendar system like the one below $($or similar to it$)$ taking into account the following:

$1-$ The dates and days are computed using PHP dates functions.

$2-$ The user will be able to click some date, upon clicking, s$/$he will be able to add some text to be saved$/$retrieved in$/$from a database.

I want the easiest way to solve it in a simplified way