The Project | About Us | Contribute | Donations | License
HOME My courses Completed
◄ Previous
◄

Loops in PHP

Next ►
►

Loops are fundamental constructs in programming that allow you to execute a block of code multiple times. PHP supports several types of loops, each suited for different scenarios. In this section, we will cover the following types of loops:

  1. while Loop
  2. do-while Loop
  3. for Loop
  4. foreach Loop

  1. while Loop

The while loop executes a block of code as long as a specified condition is true.

Syntax

while (condition) {
    // Code to be executed
}

Example

<?php
$counter = 1;

while ($counter <= 5) {
    echo "Counter is at: $counter\n";
    $counter++;
}
?>

Explanation

  • Initialization: $counter = 1; initializes the counter variable.
  • Condition: while ($counter <= 5) checks if the counter is less than or equal to 5.
  • Increment: $counter++; increments the counter by 1 in each iteration.

Output

Counter is at: 1
Counter is at: 2
Counter is at: 3
Counter is at: 4
Counter is at: 5

  1. do-while Loop

The do-while loop is similar to the while loop, but it guarantees that the block of code will be executed at least once.

Syntax

do {
    // Code to be executed
} while (condition);

Example

<?php
$counter = 1;

do {
    echo "Counter is at: $counter\n";
    $counter++;
} while ($counter <= 5);
?>

Explanation

  • The block of code inside the do section is executed first.
  • After the block is executed, the condition ($counter <= 5) is checked.

Output

Counter is at: 1
Counter is at: 2
Counter is at: 3
Counter is at: 4
Counter is at: 5

  1. for Loop

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

Syntax

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

Example

<?php
for ($counter = 1; $counter <= 5; $counter++) {
    echo "Counter is at: $counter\n";
}
?>

Explanation

  • Initialization: $counter = 1; initializes the counter variable.
  • Condition: $counter <= 5; checks if the counter is less than or equal to 5.
  • Increment: $counter++; increments the counter by 1 in each iteration.

Output

Counter is at: 1
Counter is at: 2
Counter is at: 3
Counter is at: 4
Counter is at: 5

  1. foreach Loop

The foreach loop is used to iterate over arrays. It is particularly useful for associative arrays.

Syntax

foreach ($array as $value) {
    // Code to be executed
}

Example

<?php
$fruits = array("Apple", "Banana", "Cherry");

foreach ($fruits as $fruit) {
    echo "Fruit: $fruit\n";
}
?>

Explanation

  • The foreach loop iterates over each element in the $fruits array.
  • In each iteration, the current element is assigned to the $fruit variable.

Output

Fruit: Apple
Fruit: Banana
Fruit: Cherry

Associative Array Example

<?php
$person = array("Name" => "John", "Age" => 30, "City" => "New York");

foreach ($person as $key => $value) {
    echo "$key: $value\n";
}
?>

Explanation

  • The foreach loop iterates over each key-value pair in the $person array.
  • In each iteration, the current key is assigned to the $key variable, and the current value is assigned to the $value variable.

Output

Name: John
Age: 30
City: New York

Practical Exercises

Exercise 1: Sum of Numbers

Write a PHP script that calculates the sum of numbers from 1 to 10 using a for loop.

Solution

<?php
$sum = 0;

for ($i = 1; $i <= 10; $i++) {
    $sum += $i;
}

echo "The sum of numbers from 1 to 10 is: $sum\n";
?>

Exercise 2: Display Even Numbers

Write a PHP script that displays all even numbers between 1 and 20 using a while loop.

Solution

<?php
$number = 1;

while ($number <= 20) {
    if ($number % 2 == 0) {
        echo "$number\n";
    }
    $number++;
}
?>

Exercise 3: Iterate Over an Associative Array

Write a PHP script that iterates over an associative array and prints both the keys and values.

Solution

<?php
$student = array("Name" => "Alice", "Grade" => "A", "Subject" => "Math");

foreach ($student as $key => $value) {
    echo "$key: $value\n";
}
?>

Common Mistakes and Tips

  • Infinite Loops: Ensure that the loop's condition will eventually become false. Otherwise, you may create an infinite loop.
  • Off-by-One Errors: Be careful with the loop's start and end conditions to avoid off-by-one errors.
  • Array Iteration: When using foreach with associative arrays, remember to use both key and value variables.

Conclusion

In this section, we covered the different types of loops in PHP: while, do-while, for, and foreach. Each loop type has its specific use cases and advantages. Understanding how to use these loops effectively will help you write more efficient and readable code. In the next section, we will explore switch statements, which provide a way to execute different parts of code based on the value of a variable.

◄ Previous
◄
Next ►
►

PHP Programming Course

Module 1: Introduction to PHP

Module 2: Control Structures

Module 3: Functions

Module 4: Arrays

Module 5: Working with Forms

Module 6: Working with Files

Module 7: Object-Oriented Programming (OOP)

Module 8: Working with Databases

Module 9: Advanced PHP Techniques

Module 10: PHP Frameworks and Best Practices

Module 11: Project: Building a Web Application

The Project | About Us | Contribute | Donations | License
© Copyright 2024. All rights reserved