Introduction to While Loop in PHP
As we all know that PHP is one of the most widely used languages for web development. Understanding the basic concepts is very important in any programming language before diving deep into the advanced ones. Loops are one of the largely and most commonly used while writing any piece of code as their main purpose is to execute the same piece of code repeatedly according to specific requirements of a programmer. Code/statements inside the while loop in PHP execute until the programmer’s condition remains ‘true’. There is no need to specify the exact number of iterations for which a while loop should run, unlike ‘for’ loops.
Below mentioned is the syntax of while loop in PHP:
Syntax:
while (condition to be true)
{
..
..
// Set of Statements to be executed
..
..
..
}
Statements inside the while loop will not execute once the loop’s condition is evaluated to be false.
Flowchart:
Below given is the basic flowchart expressing the process of how the while loop performs its action.
How While Loop works in PHP?
As explained above, while loop works until the condition specified is satisfied. Working of while loop in PHP is explained in the below steps:
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- First, the condition given inside the brackets after the while keyword is checked.
- If the condition is satisfied or is true, then the control is moved inside the loop.
- The statements inside the loop are executed.
- Once all the statements inside the loop are executed, the condition is checked again, and if it is true, the execution continues.
- When the condition is evaluated to be false, the control will not move inside the loop, and the while loop terminates.
Examples of While Loop in PHP
Below are the different examples of while loop in PHP:
Example #1 – Printing the value of a field according to the specific condition.
Code:
<!DOCTYPE html>
<html>
<head>
<title>PHP while Loop Example 1</title>
</head>
<body>
<?PHP
$value = 10;
while ((int)$value > 5) {
echo "The value of the field is : $value <br>";
$value--;
}
?>
</body>
</html>
Output:
The value of the field is 10
The value of the field is 9
The value of the field is 8
The value of the field is 7
The value of the field is 6
Explanation
In the above program, a variable with the name ‘value’ is assigned with the value 10. Now the while loop condition is checked, i.e. 10 > 5, which is true, so the statements inside the loop will execute. The value of variable ‘value’ is decreased by 1 and again checked with the while condition. Execution of statements inside the while loop continues until the value of the variable becomes 6. Once the value becomes 5 and the condition evaluates to be false (5 > 5), the while loop terminates, and the echo statement inside the while loop will not execute.
Example #2 – Printing the sum of digits of a given number.
Code:
<!DOCTYPE html>
<html>
<head>
<title>PHP while Loop Example 2</title>
</head>
<body>
<?PHP
$number = 107;
$sum=0; $rem=0;
while((int)$number != 0)
{
$rem=$number%10;
$sum = $sum + $rem;
$number=$number/10;
}
echo "The Sum of digits of number given 107 is $sum";
?>
</body>
</html>
Output:
The Sum of digits of the number given 107 is 8
Explanation
In the above example, the sum of the digits of the number ‘107’ is calculated, which is 1+0+7. First the condition of while loop, i.e. 107 != 0, is checked. As the condition evaluates to be true, control will move inside the loop remainder (rem) is calculated (107%10), i.e. 7 and is added to the sum variable, which becomes 0+7 =7. Number now becomes 107/10 = 10. Again the number 10 is checked against the while condition, which is set to be true, and the control will again move inside the loop. Rem variable now is 10%10 =0 and sum becomes 7+ 0 = 7 . number variable now becomes 10/10 =1, which is again not equal to 0 and move inside the while loop, so the rem variable becomes 1%10 =1. sum =7+1 =8. Number variable becomes 1/10 =0. Now the while condition is evaluated to be false, so the cursor will not move inside the while loop, and the sum final value becomes 8, which is printed on the screen.
Example #3 – Generate and print the table of number 6.
Code:
<!DOCTYPE html>
<html>
<head>
<title>PHP while Loop Example 2</title>
</head>
<body>
<?PHP
$table_number= 6;
$mult =1;
while((int)$mult<=10)
{
echo "$table_number * $mult <br>";
$mult++;
}
?>
</body>
</html>
Output:
6
12
18
24
30
36
42
48
54
60
Explanation
In the above program, the table of the variable, ‘table_number’, is printed. In general, a number whose table needs to be printed remains the same, i.e. 6 in this case, whereas the multiples keep on incrementing from 1 till 10. For the first time, when the value of the ‘mult’ variable is 1, so the condition of while loop, i.e. 1<=10, sets to be true, and the cursor will move inside the loop, and the value of 6 * 1= 6 is printed on the screen. The value of the ‘mult’ variable is incremented by 1, i.e. now mult =2. Again, the while loop condition, i.e. 2 <=10, is checked, and the multiplication table of 6 is printed until the ‘mult’ variable is less than equal to 10. Once the value of the ‘mult’ variable becomes 11, the cursor will not move inside the loop, and the execution of the loop terminates.
Conclusion
The above explanation clearly describes the syntax of a while loop along with its working in a program. Though there are 4 types of loops used in PHP, and every loop is used in a particular situation. The programmer mainly uses a loop when the iterations are not fixed, and we need to execute the set of statements until the main condition is evaluated. It is important to understand the working of loops before using them, as partial knowledge of them can sometimes lead to unexpected results.
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