In thinking about your situation a question arose: why do think you need to use MySQL for your purpose? Do you know what a relational database is?

According to your posted code, you are only tracking 4 pieces of data: name, phone number and birthday (plus an added ID field, which I don't see the purpose of).

So what could be simpler than a plain text file formatted as CSV or whatever?

For example:
id1|my name|yyyymmdd|nnnnnnnnnn
id2|your name|yyyymmdd|nnnnnnnnnn
id3|his name|yyyymmdd|nnnnnnnnnn
id4|her name|yyyymmdd|nnnnnnnnnn

You can use PHP's native string / regex functions to find whatever you want.

Using a relational database for such a simple task is like using a sledge hammer to put in a 1" finishing nail.