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PHP Looping

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>

The for Statement

The for statement is used when you know how many times you want to execute a statement or a list of statements.

Syntax

for (initialization; condition; increment)
{
  code to be executed;
}

Note: The for statement has three parameters. The first parameter initializes variables, the second parameter holds the condition, and the third parameter contains the increments required to implement the loop. If more than one variable is included in the initialization or the increment parameter, they should be separated by commas. The condition must evaluate to true or false.

Example

The following example prints the text "Hello World!" five times:

<html>
<body>

<?php
for ($i=1; $i<=5; $i++)
{
  echo "Hello World!<br />";
}
?>

</body>
</html>

The foreach Statement

The foreach statement is used to loop through arrays.

For every loop, the value of the current array element is assigned to $value (and the array pointer is moved by one) - so on the next loop, you'll be looking at the next element.

Syntax

foreach (array as value)
{
    code to be executed;
}

Example

The following example demonstrates a loop that will print the values of the given array:

<html>
<body>

<?php
$arr=array("one", "two", "three");

foreach ($arr as $value)
{
  echo "Value: " . $value . "<br />";
}
?>

</body>
</html>

Viewed:284

14-Jul-2008
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