Different loops in PHP
Copyright © 2005-2006 Amrit Hallan
The PHP programming language primarily has 4 loops:
* while()
* do{…}while()
* for()
* foreach()
An example of while loop is:
== Code begins ==
<?php
$keeplooping=0;
while($keeplooping<10)
{
print "This is loop number " . ($keeplooping + 1) . ".<br>";
$keeplooping++;
}
?>
== Code ends ==
The result of this code is:
This is loop number 1.
This is loop number 2.
This is loop number 3.
This is loop number 4.
This is loop number 5.
This is loop number 6.
This is loop number 7.
This is loop number 8.
This is loop number 9.
This is loop number 10.
As it is understood by the language, the while() loop first checks the
condition, and only executes the commands within its periphery if the
condition for the execution of the loop is satisfied. In the above case, the
value of $keeplooping has to be less than 10 if you want the loop to happen.
So if you had initialized $keeplooping = 10, the loop wouldn’t have
executed. Now we apply the same code to the do{…}while() loop and see what
happens.
== Code begins ==
<?php
$keeplooping=10;
do{
print "This is loop number " . ($keeplooping + 1) . ".<br>";
$keeplooping++;
}while($keeplooping<10)
?>
== Code ends ==
The result of this code is:
This is loop number 11.
The do{…}while() loop executes the lines at least once before checking for
the condition. This loop first executes, and then checks, and the previous
loop first checks and then executes.
Now we come to the for() loop. This loop is like the while(). The difference
is, it generally initializes the loop controlling condition within its
bracket. The following code explains this loop.
== Code begins ==
<?php
for($i=0; $i<10; $i++)
{
print "This is loop number " . ($i+1) . ".<br>";
}
?>
== Code ends ==
The result of this code is:
This is loop number 1.
This is loop number 2.
This is loop number 3.
This is loop number 4.
This is loop number 5.
This is loop number 6.
This is loop number 7.
This is loop number 8.
This is loop number 9.
This is loop number 10.
The three parameters of this loop are self-explanatory. The first portion
initializes the conditioning variable ($i=0), the second portion checks
whether the condition is still conducive for the execution of the loop
($i<10) and the third portion keeps incrementing the variable until it
exceeds the allowed limit ($i++). You can also leave one or more parameters
blank such as:
== Code begins ==
<?php
for($i=0; $i<10;)
{
print "This is loop number " . ($i+1) . ".<br>";
$i++;
}
?>
== Code ends ==
gives you the same result as the previous example.
Lastly, we come to the foreach() loop. You can see an application of this
loop at
http://www.aboutwebdesigning.com/2005/11/07/associative-arrays-in-php. This
loop is used while going through an associative array. Its syntax is like
this:
== Code begins ==
<?php
foreach($ass_array as $key => $value)
{
print "The index position right now is " . $key . " and its value is
" . $value . ".<br>";
}
?>
== Code ends ==
$ass_array is the associative array here. As you already know (explained in
the above mentioned link) that associative arrays have string names as
reference to their index positions, $key holds the string value of the index
position. $value holds the actual value that the array holds at the $key
index position.
Amrit Hallan is a freelance copywriter,
and a website content writer. He also dabbles
with PHP and HTML. For more tips and tricks in
PHP, JavaScripting, XML, CSS designing and
HTML, visit his blog at
http://www.aboutwebdesigning.com
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