PHP Loops – Complete Guide with Examples

Welcome to phponline.in, your trusted source to master PHP programming step by step.

In this chapter, we will cover one of the most powerful concepts in PHP — Loops.

Loops are essential in PHP because they help us execute a block of code repeatedly, reducing redundancy and improving performance.

From printing sequences of numbers to iterating over arrays and objects, loops are everywhere in real-world PHP projects like:

Login systems
Shopping carts
Data-driven dashboards
API processing
CMS development

Let’s dive deep into PHP loops with syntax, examples, real-world use cases, and best practices.

You will Learn

Introduction to Loops in PHP
Why Use Loops in PHP?
Types of Loops in PHP
The while Loop in PHP
The do...while Loop
The for Loop
The foreach Loop
Nested Loops in PHP
Loop Control Statements (break, continue)
Infinite Loops in PHP
Using Loops with Arrays
Using Loops with Associative Arrays
Using Loops with Multidimensional Arrays
Loops and Functions
Loops in Real-World Applications
Performance Considerations with Loops
Best Practices for Writing PHP Loops
PHP Loops vs Recursion
Common Mistakes in Loops
Alternative Syntax of Loops in PHP

1. Introduction to Loops in PHP

In programming, a loop is a control structure that allows you to execute a block of code multiple times automatically until a condition is false.

For example:

$count = 1;
while ($count <= 5) {
    echo "Count is: $count <br>";
    $count++;
}

Output:

Count is: 1  
Count is: 2  
Count is: 3  
Count is: 4  
Count is: 5

2. Why Use Loops in PHP?

Imagine needing to display numbers 1 to 100. Without loops, you’d have to write 100 echo statements! Loops save time, reduce code length, and increase efficiency.

Real-world use cases:

Printing database records
Processing forms
Running batch operations
Displaying menus dynamically

3. Types of Loops in PHP

PHP provides four main loops:

while loop
do...while loop
for loop
foreach loop

Additionally, you can nest loops and use control statements to manage them.

4. PHP while Loop

Syntax:

while (condition) {
    // code to execute
}

Example:

$number = 1;
while ($number <= 5) {
    echo "Number: $number <br>";
    $number++;
}

5. PHP do…while Loop

Executes code at least once, then checks condition.

$number = 1;
do {
    echo "Number: $number <br>";
    $number++;
} while ($number <= 5);

6. PHP for Loop

Best when you know the number of iterations.

for ($i = 1; $i <= 5; $i++) {
    echo "Iteration: $i <br>";
}

7. PHP foreach Loop

Designed for arrays & collections.

$fruits = ["Apple", "Banana", "Orange"];
foreach ($fruits as $fruit) {
    echo "$fruit <br>";
}

With keys:

$users = ["id1" => "Alice", "id2" => "Bob"];
foreach ($users as $id => $name) {
    echo "$id => $name <br>";
}

8. Nested Loops in PHP

Loops inside loops.

for ($i = 1; $i <= 3; $i++) {
    for ($j = 1; $j <= 3; $j++) {
        echo "($i, $j) ";
    }
    echo "<br>";
}

9. Loop Control Statements

break; → Exit loop early
continue; → Skip current iteration

Example:

for ($i = 1; $i <= 5; $i++) {
    if ($i == 3) continue;
    echo "Number: $i <br>";
}

10. Infinite Loops in PHP

Dangerous but sometimes useful (e.g., daemon scripts).

while (true) {
    echo "Running...";
    break; // prevent actual infinite loop
}

11. Using Loops with Arrays

$numbers = [1, 2, 3, 4, 5];
for ($i = 0; $i < count($numbers); $i++) {
    echo $numbers[$i] . "<br>";
}

12. Using Loops with Associative Arrays

$student = ["Name" => "John", "Age" => 20, "Grade" => "A"];
foreach ($student as $key => $value) {
    echo "$key: $value <br>";
}

13. Using Loops with Multidimensional Arrays

$students = [
    ["John", 20, "A"],
    ["Alice", 22, "B"],
    ["Bob", 19, "C"]
];

foreach ($students as $student) {
    foreach ($student as $detail) {
        echo $detail . " ";
    }
    echo "<br>";
}

14. Loops and Functions

You can use loops inside functions.

function printNumbers($limit) {
    for ($i = 1; $i <= $limit; $i++) {
        echo $i . " ";
    }
}
printNumbers(10);

15. Real-World Applications of PHP Loops

Generating tables dynamically
Reading database results
Processing API responses
Building pagination
Creating reports

16. Performance Considerations with Loops

Minimize calls to count() inside loops
Use foreach for arrays (faster)
Avoid unnecessary nesting

17. Best Practices for Writing Loops

Use descriptive variable names
Always define loop exit conditions
Keep loops optimized for performance

18. PHP Loops vs Recursion

Loops → Iterative
Recursion → Function calling itself

Loops are generally faster, recursion better for tree/graph problems.

19. Common Mistakes in Loops

Infinite loops due to missing increment
Off-by-one errors (<= vs <)
Overusing nested loops

20. Alternative Syntax in Loops

Great for embedding PHP in HTML.

<?php for ($i = 1; $i <= 5; $i++): ?>
    <p>Item <?= $i ?></p>
<?php endfor; ?>

PHP loops, PHP while loop, PHP for loop, PHP foreach loop, PHP do while loop, PHP nested loops, PHP control structures, PHP programming basics

Realted

Frequently Asked Questions (FAQ)

Q1: Which loop is best for arrays in PHP?
A: The foreach loop is best for arrays because it’s simple and efficient.

Q2: Can I break out of nested loops?
A: Yes, by using break 2; to exit two levels.

Q3: What is the difference between while and do...while?
A: while checks condition first, do...while executes at least once before checking.

Q4: Are infinite loops bad?
A: Yes, unless controlled (e.g., with break or in background workers).