PHP Program to Print Numbers 1 to n

Use a for loop in PHP like for ($i = 1; $i <= $n; $i++) { echo $i . "\n"; } to print numbers from 1 to n.

Examples

Input1

Output1

Input5

Output1 2 3 4 5

Input0

Output

How to Think About It

To print numbers from 1 to n, start counting from 1 and keep increasing by 1 until you reach n. For each number, print it on a new line. If n is zero or negative, print nothing.

Algorithm

1

Get the input number n.

2

Start a counter i at 1.

3

While i is less than or equal to n, do the following:

4

Print the current value of i.

5

Increase i by 1.

6

Stop when i becomes greater than n.

Code

php

<?php
$n = 5; // You can change this value
for ($i = 1; $i <= $n; $i++) {
    echo $i . "\n";
}
?>

Output

1
2
3
4
5

Dry Run

Let's trace the program with n = 3 through the code

1

Initialize n and i

n = 3, i = 1

2

Check condition i <= n

1 <= 3 is true, so enter loop

3

Print i

Print 1

4

Increment i

i becomes 2

5

Repeat condition check

2 <= 3 is true, print 2, increment i to 3

6

Repeat condition check

3 <= 3 is true, print 3, increment i to 4

7

Condition fails

4 <= 3 is false, exit loop

i	Condition i <= n	Action
1	true	Print 1, i++ to 2
2	true	Print 2, i++ to 3
3	true	Print 3, i++ to 4
4	false	Exit loop

Why This Works

Step 1: Initialize counter

We start counting from 1 using $i = 1 because we want to print from 1 to n.

Step 2: Loop condition

The loop runs while $i <= $n to ensure we print all numbers up to n.

Step 3: Print and increment

Inside the loop, we print the current number and then increase $i by 1 to move to the next number.

Alternative Approaches

while loop

php

<?php
$n = 5;
$i = 1;
while ($i <= $n) {
    echo $i . "\n";
    $i++;
}
?>

Uses a while loop instead of for; functionally the same but some find for loops cleaner for counting.

do-while loop

php

<?php
$n = 5;
$i = 1;
do {
    echo $i . "\n";
    $i++;
} while ($i <= $n);
?>

Ensures the loop runs at least once; useful if you want to print at least one number even if n is less than 1.

recursive function

php

<?php
function printNumbers($i, $n) {
    if ($i > $n) return;
    echo $i . "\n";
    printNumbers($i + 1, $n);
}
printNumbers(1, 5);
?>

Uses recursion to print numbers; elegant but less efficient and can cause stack overflow for very large n.

Complexity: O(n) time, O(1) space

Time Complexity

The loop runs exactly n times, so the time grows linearly with n, making it O(n).

Space Complexity

The program uses a fixed amount of memory regardless of n, so space complexity is O(1).

Which Approach is Fastest?

The for loop and while loop have similar performance; recursion is slower and uses more memory.

Approach	Time	Space	Best For
for loop	O(n)	O(1)	Simple and clear counting
while loop	O(n)	O(1)	Similar to for, flexible condition
do-while loop	O(n)	O(1)	At least one iteration guaranteed
recursive function	O(n)	O(n)	Elegant but uses more memory