PHP Loops
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 lines in a script we can use loops
to perform a task like this.
In PHP, we
have the following looping statements:
- while - loops
through a block of code while a specified condition is true
- do...while - loops
through a block of code once, and then repeats the loop as long as a
specified condition is true.
Deleting spam email, sealing 50 envelopes, and going to
work are all examples of tasks that are repeated.
The nice thing about programming is that you can avoid
such repetitive tasks with a little bit of extra thinking.
Most often these repetitive tasks are conquered in the loop.
The idea of a loop is to do something over and over
again until the task has been completed.
Before we show a real example of when you might need
one, let's go over the structure of the PHP while loop.
1)Simple
While Loop Example
The
function of the while loop is to do a task over and over as long as the
specified conditional statement is true.
This
logical check is the same as the one that appears in a PHP if statement to
determine if it is true or false.
Here is
the basic structure of a PHP while loop:
Syntax:
while (condition)
{
code to be executed;
}
Example:
<html>
<body>
<?php
$i=1;
while($i<=5)
{
echo "The number is " . $i . "<br>";
$i++;
}
?>
</body>
</html>
Output:
The number is 1
The number is 2
The number is 3
The number is 4
The number is 5
2)The do...while Statement
The
do...while statement will always execute the block of code once, it will then
check the condition, and repeat the loop while the condition is true.
A "do
while" loop is a slightly modified version of the while loop.
If you
recall from one of the previous lessons on While Loops the conditional
statement is checked comes back true then the code within the while loop is
executed.
If the conditional statement is false then the
code within the loop is not executed.
Syntax:
do
{
code to be executed;
}
while (condition);
Examples:
<html><body> <?php $x=1; do { $x++; echo "The number is " . $x . "<br />"; } while ($x<=5);?> </body></html>
Output: The number is 2The number is 3The number is 4The number is 5The number is 6
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