Often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost equal code-lines in a script, we can use loops to perform a task like this.The point about the speed in loops is, that the middle and the last expression are executed EVERY time it loops. So you should try to take everything that doesn't change out of the loop.
In PHP, we have the following looping statements:
while- loops through a block of code as long as the specified condition is true
do...while- loops through a block of code once, and then repeats the loop as long as the