So why do we use loops? There are hundreds and hundreds of reasons, the widest usage is probably to cycle through values of some sort of data. For example, you might be writing a messaging system in PHP, which would allow users of your website to send private messages to each other once they register. You would write a MySQL query which would pull all the user’s letter from the database. To show all the letters you would use a loop to show all the rows of the query (all the separate messages) on a page.
To create a loop you need to add some rules which will dictate how the loop should behave. Usually we need to give three values, the starting value of the counter (which tells the loop how many times it has executed), an ending value (which tells the script to stop looping if it is reached) and an increment, which deals with changing the starting counter value in some way (so that it eventually reaches the end value, hence ending the loop).