PHP Loops

• PHP loops also called iteration.
• Iteration or looping is a way to execute a block of program statements more than once.
• we will use the for statement to create loops.
• The for loop is generally controlled by counting.
• There is an index variable that you increment or decrement each time through the loop.
• When the index reaches some limit condition, then the looping is done and we continue on in the code.

Why do we want loops in our code?

• Do something for a given number of times or for every object in a collection of objects.
• For every radio button in a form, see if it is checked.
• For every month of the year, charge $100 against the balance.
• Calculate the sum of all the numbers in a list.
• Many loops are counting loops.
• They do something a certain number of times.
  

PHP Looping :

Looping statements in PHP are used to execute the same block of code a specified number of times.
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.
• For each-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:

$i=1;
while($i<=5)
{
echo "The number is " . $i . "
";
$i++;
}


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 asa 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:

$i=0;
do
{
$i++;
echo "The number is " . $i . "
";
}
while ($i<5);


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:

for ($i=1; $i<=5; $i++)
{
echo "Hello World!
";
}


The foreach Statement:

The for eachstatement 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:

$arr=array("one", "two", "three");
foreach($arras $value)
{
echo "Value: " . $value . "
";
}