PHP Loop Structures

Repetitive tasks are always a burden to us. 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.

The ability to perform repetitive tasks is a very important aspect of any programming language. 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. Looping statements in PHP are used to execute the same block of code a specified number of times.

 
Looping

Very often when you write code, you want the same block of code to run a number of times. You can use looping statements in your code to perform this.

In PHP we have the following looping statements:

* while - loops through a block of code if and as long as a specified condition is true
* do…while - loops through a block of code once, and then repeats the loop as long as a special condition is true
* for - loops through a block of code a specified number of times
* foreach - loops through a block of code for each element in an array

 
The while Statement

The while statement will execute a block of code if and as long as a condition is true.

Syntax

while (condition)
code to be executed;

 
Example

The following example demonstrates a loop that will continue to run as long as the variable i is less than, or equal to 5. i will increase by 1 each time the loop runs:

<html>
<body>
 
<?php 
$i=1;
while($i<=5)
  {
  echo "The number is " . $i . "<br />";
  $i++;
  }
?>
 
</body>
</html>

 
The do…while Statement

The do…while statement will execute a block of code at least once - it then will repeat the loop as long as a condition is true.

Syntax

do
{
code to be executed;
}
while (condition);

 
Example

The following example will increment the value of i at least once, and it will continue incrementing the variable i as long as it has a value of less than 5:

<html>
<body>
 
<?php 
$i=0;
do
  {
  $i++;
  echo "The number is " . $i . "<br />";
  }
while ($i<5);
?>
 
</body>
</html>


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