Loops in PHP

[Priyank K. Suthar]

What is a loop?:
You've heard the term loop before, but you may not really be sure what
it is. A loop is a series of commands that will continue to repeat
over and over again untill a condition is met. For example, let's say
you have the names of people in an array, and you wanted print a list
of all of the names. You could setup a loop that would print the first
persons name, and then move on to the next and print her name, etc
(the continuing to repeat itself part.) The condition would be that it
stops once all of the names have been used.

WHILE loops

In PHP there are several different types of loops. Basically what a
loop does is evaluate a statement as true or false. If it is true it
executes some code and then alters the original statement and starts
all over again by re-evaluating it. It continues to loop through the
code like this until the statement becomes false.

Here is an example in its simplest form:

<?php
$num = 1;
while ( $num <=10 )
{
print $num . " ";
$num++;
}
?>

Basically what this does is: while a number is greater than or equal
to 10 it prints the number. The ++ adds one to the number, however
this could also be phrased as $num = $num + 1; Once the number becomes
greater than 10, in our case it becomes 11, then it stops executing
the code within the {brackets}

Below is an example of how you can combine a loop with a conditional

<?php
$num = 1;
while ( $num <=10 )
{
if ($num < 5)
{
print $num . " is less than 5 <br>";
}
else
{
print $num . " is not less than 5 <br>";
}
$num++;
}
?>

FOR Loops

A FOR loop is very similar to a WHILE loop in that it continues to
process a block of code until a statement becomes false, however
everything is defined in a single line. The basic structure for a FOR
loop is:

for ( start; conditional; increment) { code to execute; }

Let's go back to our first example using the WHILE loop, where we
printed out the numbers 1 through 10 and do the same thing using a FOR
loop.

<?php
for ($num=1; $num <= 10; $num++ )
{
print $num . " ";
}
?>

The FOR loop can also be used in conjunction with a conditional, just
like we did with the WHILE loop:

<?php
for ($num=1; $num <= 10; $num++ )
{
if ($num < 5)
{
print $num . " is less than 5 <br>";
}
else
{
print $num . " is not less than 5 <br>";
}
}
?>

FOREACH Loops

To understand FOREACH loops you have to remember what we learned about
arrays. If you recall an array (unlike a variable) contains a group of
data. When using a loop with an array, instead of having a counter
that goes until proven false the FOREACH loop continues until it has
used all values in the array. So for example if an array contained 5
pieces of data, then the FOREACH loop would execute 5 times. More uses
for arrays and FOREACH loops will become apparent when you start
importing data from MySQL.

A FOREACH loop is phrased like this: FOREACH (array as value) { what
to do; }

Here is an example of a FOREACH loop:

<?php
$a = array(1, 2, 3, 4, 5);
foreach ($a as $b)
{
print $b . " ";
}
?>

Once you understand that concept you can then use the FOREACH loop to
do more practical things. Let's say an array contains the ages of 5
family members. Then we will make a FOREACH loop that will determine
how much it costs for each of them to eat on a buffet that has varied
prices based on age. We will use the following pricing system: Under 5
is free, 5-12 years costs $4 and over 12 years is $6.

<?php
$t = 0;
$age = array(33, 35, 13, 8, 4);
foreach ($age as $a)
{
if ($a < 5)
{$p = 0;}
else
{
if ($a <12)
{$p = 4;}
else
{$p = 6;}
}
$t = $t + $p;
print "$" . $p . "<br>";
}
print "The total is: $" . $t;
?>