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. 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.
In PHP we have the following looping statements:
The while statement will execute a block of code if and as long as a condition is true.
Syntax
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:
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
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:
The for statement is used when you know how many times you want to execute a statement or a list of statements.
Syntax
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:
The foreach statement is used to loop through arrays. For every loop, the value of the current array element is assigned to $value so on the next loop.
Syntax
Example
The following example demonstrates a loop that will print the values of the given array:
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
Code:
while (condition)
{
code to be executed;
}
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:
Code:
<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
Code:
do
{
code to be executed;
}
while (condition);
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:
Code:
<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
Code:
for (initialization; condition; increment)
{
code to be executed;
}
Example
The following example prints the text "Hello World!" five times:
Code:
<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 so on the next loop.
Syntax
Code:
foreach (array as value)
{
code to be executed;
}
The following example demonstrates a loop that will print the values of the given array:
Code:
<html>
<body>
<?php
$arr=array("one", "two", "three");
foreach ($arr as $value)
{
echo "Value: " . $value . "<br />";
}
?>
</body>
</html>
