Lesson 5 • Beginner

Loops 🔁

Repeat code efficiently with for, while, do-while, and foreach — PHP's most powerful and frequently used loop.

What You'll Learn in This Lesson

• For loop for counted iterations
• While and do-while for condition-based loops
• Foreach for iterating arrays (PHP's most-used loop)
• Break and continue to control loop flow
• Nested loops and real-world order processing examples

Note: PHP runs on a server. Our examples simulate PHP logic using JavaScript. To run real PHP, install PHP.

🎯 Real-World Analogy: Loops are like a factory assembly line. A for loop is like saying "make exactly 100 widgets." A while loop is "keep making widgets until the material runs out." A foreach loop is "inspect every widget in this box."

1️⃣ Loop Types at a Glance

Loop	Best For	Syntax
for	Known number of iterations	for ($i=0; $i<10; $i++)
while	Unknown iterations, check first	while ($condition)
do-while	Run at least once	do while ($cond)
foreach	Iterate arrays (most common!)	foreach ($arr as $v)

Try It: Basic Loops

Practice for, while, do-while, and foreach loops with real examples

Try it Yourself »

JavaScript

// PHP Loops (simulated in JavaScript)
console.log("=== For Loop ===");
console.log();
console.log("Syntax: for ($i = 0; $i < count; $i++) { ... }");
console.log();

// for loop — when you know how many times to loop
for (let i = 1; i <= 5; i++) {
    console.log("  Iteration " + i + ": " + "⭐".repeat(i));
}

console.log();
console.log("=== While Loop ===");
console.log();
console.log("Syntax: while ($condition) { ... }");
console.log("Use when you DON'T know how many iterations.");
console.log(
...

Try It: Advanced Loops

Nested loops, break/continue, and a real-world order processing system

Try it Yourself »

JavaScript

// Advanced Loop Patterns in PHP
console.log("=== Nested Loops: Multiplication Table ===");
console.log();

// Build a 5x5 multiplication table
let header = "  × |";
for (let i = 1; i <= 5; i++) header += ("  " + i).slice(-3);
console.log(header);
console.log("  ──┼───────────────");

for (let i = 1; i <= 5; i++) {
    let row = ("  " + i).slice(-2) + " |";
    for (let j = 1; j <= 5; j++) {
        row += ("  " + (i * j)).slice(-3);
    }
    console.log(row);
}

console.log();
console.log("===
...

⚠️ Common Mistakes

⚠️

Infinite loops — forgetting to increment the counter or update the condition. Always ensure the loop can terminate!

⚠️

Off-by-one errors — using <= vs <. Decide: do you start at 0 or 1?

⚠️

Modifying array inside foreach — can cause unexpected behaviour. Use a separate array for modifications.

💡

Pro Tip: Always use foreach for arrays in PHP — it's faster, cleaner, and less error-prone than for with index.

📋 Quick Reference — PHP Loops

Statement	Purpose
for ($i=0; $i<n; $i++)	Loop n times
foreach ($arr as $v)	Iterate values
foreach ($arr as $k=>$v)	Iterate key-value pairs
break	Exit loop immediately
continue	Skip to next iteration

🎉 Lesson Complete!

You've mastered PHP loops! Next, learn how to write reusable functions.