In the previous chapter we've learned how to create a database on MySQL server. Now it's time to create some tables inside the database that will actually hold the data. A table organizes the information into rows and columns.
The PHP code in the above example creates a table named persons with four columns id, first_name, last_name and email inside the demo database.
Notice that each field name is followed by a data type declaration; this declaration specifies what type of data the column can hold, whether integer, string, date, etc.
There are a few additional constraints (also called modifiers) that are specified after the column name in the preceding SQL statement, like NOT NULL, PRIMARY KEY, AUTO_INCREMENT, etc. Constraints define rules regarding the values allowed in columns.