PHP Loop Types ~ gwax programs

Loops in PHP are used to execute the same block of code a specified number of times. PHP
supports following four loop types.

for - loops through a block of code a specified number of times.
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.
foreach - loops through a block of code for each element in an array.
We will discuss in next tutorial about continue and break keywords used to control the loops execution.

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

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

The initializer is used to set the start value for the counter of the number of loop iterations. A
variable may be declared here for this purpose and it is traditional to name it $i.
Example
The following example makes five iterations and changes the assigned value of two variables on
each pass of the loop:

<html>
<body>
<?php
$a = 0;
$b = 0;
for( $i=0; $i<5; $i++ )
{
$a += 10;
$b += 5;
}
echo ("At the end of the loop a=$a and b=$b" );
?>
</body>
</html>

This will produce following result:

At the end of the loop a=50 and b=25

The while loop statement
The while statement will execute a block of code if and as long as a test expression is true.
If the test expression is true then the code block will be executed. After the code has executed
the test expression will again be evaluated and the loop will continue until the test expression is
found to be false.

Syntax

while (condition)
{
code to be executed;
}

Example
This example decrements a variable value on each iteration of the loop and the counter
increments until it reaches 10 when the evaluation is false and the loop ends.

<html>
<body>
<?php
$i = 0;
$num = 50;
while( $i < 10)
{
$num--;
$i++;
}
echo ("Loop stopped at i = $i and num = $num" );
?>
</body>
</html>

This will produce following result:

Loop stopped at i = 1 and num = 40

The do...while loop 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 10:

<html>
<body>
<?php
$i = 0;
$num = 0;
do
{
$i++;
}while( $i < 10 );
echo ("Loop stopped at i = $i" );
?>
</body>
</html>

This will produce following result:

Loop stopped at i = 10

The foreach loop statement
The foreach statement is used to loop through arrays. For each pass the value of the current
array element is assigned to $value and the array pointer is moved by one and in the next pass
next element will be processed.

Syntax

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

Example
Try out following example to list out the values of an array.

<html>
<body>
<?php
$array = array( 1, 2, 3, 4, 5);
foreach( $array as $value )
{
echo "Value is $value <br />";
}
?>
</body>
</html>

This will produce following result:

Value is 1
Value is 2
Value is 3
Value is 4
Value is 5

About Gwax Henry

Im a Software Engineer from Tanzania specializin in Web developer, design , programming web applications.

PHP Loop Types

About Gwax Henry

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