PHP Tutorial – Lesson 3: Introduction to PHP – Part I

Loops

•          As we explained before, PHP syntax is similar to C/C++ and PERL.
•          Loops at PHP, Not at all, are same as any loop in C/C++. But also, has a special type of loop will be illustrated when using arrays.
While Loop
•          Sometimes you need a block of instructions to be repeated, as long as some condition is true.
•          Here is an example
<?php
$x = 1;
while($x<10)
{
echo $x.”  “;
$x++;
}
?>
•          Previous script is a simple application, that prints numbers from 1 to 9. as a programmer, you should be familiar with this kind of loop.
Do… While Loop
•          In some cases you might want some instructions to be executed at least once, and be repeated as long as condition is true, best choice of loop here to be chosen is do … while loop.
<?php
$i=1;
do {
$i++;
echo $i.” “;
} while($i <10);
?>
•          Previous script prints numbers from 2 to 9.
For Loop
•          Often, for loop is used when you know how many times shall the loop run.
•          Syntax:
•          for(init,condition,increment)
•          Init: is the code to be executed at beginning of the loop, it is executed once. Init could be any php statement, and might be more than one statement, but should be separated by commas ,
•          Condition: the case that makes loop run.
•          Increment: is the code to be executed at each time the loop run, as init it might be more than one statement.
Advices
•          As a programmer, it is your responsible to determine, what is the best kind of loops to be chosen for your case.
•          If you know exactly your script how many times should be run. Then the best choice of loop here will be for loop.
•          If you don’t know how many times the script should be run, or it depends on user inputs, then best choice here while or do… while loop.
•          If your script should be executed at least one time, then do … while is the best choice.
•          If your script should be executed at most one time, then there is no need for loop!
•          Latest type of loops that is special, or is one of the powerful properties of php, is foreach loop.
•          This kind of loop is the best choice when you deal with arrays.
•          Arrays will be discussed next Lesson.
To download this Lesson as PDF file click here: PHP Tutorial – Lesson 3: Introduction to PHP – Part I
Best Wishes,
Anas Jaghoub
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