The for loop

Learn to write operations that repeat a fixed number of times with the for loop.

The for loop

The for loop is used to repeat an action a fixed number of times. It has three parts: a starting value, a condition and an increment. These parts are separated by semicolons and written inside parentheses.

For example, for ($i = 1; $i <= 3; $i++) makes $i start at 1, grow by 1 each step and keep looping while it is 3 or less. The loop body goes inside curly braces.

Counter and step

The counter is the variable that tracks which step the loop is on; it is usually named $i. In the increment part you can increase it by one with $i++.

You can also count down: for ($i = 3; $i >= 1; $i--) runs the loop for 3, then 2, then 1. To change the step size you can use compound assignment like $i += 2.

Exercise Print from 1 to 5

Use a for loop to print the numbers from 1 to 5, one per line, with echo.

Show example solution

Build the loop with for ($i = 1; $i <= 5; $i++) and print echo $i . "\n".
Example solution:
<?php
// Numbers from 1 to 5
for ($i = 1; $i <= 5; $i++) {
    echo $i . "\n";
}

Test yourself

What is the output of the loop below?
```
for ($i = 1; $i <= 3; $i++) {
    echo $i;
}
```
- 123
- 321
- 111
- 1234
Show answer

123 — Correct. $i becomes 1, 2 and 3 in turn, so 123 is printed.

Write the start of the countdown loop

for (____; $i >= 1; $i--) {
    echo $i;
}

Show answer

for ($i = 5; $i >= 1; $i--) {
    echo $i;
}

Match each for part to its meaning

$i = 1

Starting value
$i <= 5

Condition
$i++

Increment
How many times does for ($i = 10; $i >= 1; $i--) run?
```
for ($i = 10; $i >= 1; $i--) {
    echo $i;
}
```
- 9
- 11
- 10
- Infinite
Show answer

10 — Correct. There are 10 steps from 10 down to 1.

Next lesson: The while loop

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