PHP Repeating Number Triangle Pattern (Descending)

Beginner
5 min read
Updated: Sep 2026
3 programs
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Descending repeating number triangle 5, 44, 333, 2222, 11111 in PHP
Definition

What Is This Pattern?

A descending repeating number triangle prints digit i repeated rows - i + 1 times, counting i down from rows.

Remember
Rule: for i = n..1, print i exactly (n - i + 1) times

5
44
333
2222
11111   ← 5 rows

In PHP you solve it with two nested for loops: the outer loop picks the digit, the inner loop repeats it with echo $i, then echo PHP_EOL ends the row. Program 9 is the ascending twin (1, 22, 333…).

Approach

How to Solve It

Outer loop counts down from $rows to 1. Inner loop repeats digit $i exactly $rows - $i + 1 times. End each row with echo PHP_EOL.

MethodIdeaBest for
Nested loopsOuter picks digit n..1; inner repeats it n-i+1 timesLearning, interviews, exams
str_repeatBuild each full row in one callLeaner demos once loops click

Pseudocode

Pseudocode
for i from rows down to 1:
    for j from rows down to i:
        print i (no newline)
    print newline

Cheat sheet

GoalPattern
Pick digit (count down)for ($i = $rows; $i >= 1; $i--)
Repeat digit $ifor ($j = $rows; $j >= $i; $j--) echo $i;
End the rowecho PHP_EOL;
str_repeat formecho str_repeat((string) $i, $rows - $i + 1) . PHP_EOL;
Ascending twin (Program 9)for ($i = 1; $i <= $rows; $i++) with echo $i repeated $i times

Printing Numbers vs Starting a New Line

APIEffectUse for
echo $iStays on the same lineEach repeat of digit $i
echo PHP_EOLEnds the current lineAfter the inner loop

Print all repeats without a newline, then end the row once.

Try it

Live Preview

Change the row count and the repeating triangle updates instantly — capped at 9 so every digit stays a single character.

Whole numbers from 1 to 9 (single digits). Tap a chip or type a value — the preview redraws as you go.

Live result 5 rows · 15 digits
5
44
333
2222
11111
Trace

Worked Walkthrough

Trace $rows = 4 — each outer-loop value of $i, how many times the inner loop runs, and the printed row.

$iInner $jRepeatsPrinted row
44..414
34..3233
24..23222
14..141111

Total digits are 1+2+3+4 = 10 — the triangular number n(n+1)/2.

Code

PHP Programs

Three complete programs: fixed height, CLI input, and a str_repeat shortcut. Use View Output for sample results.

Example 1 — Fixed $rows = 5

Outer loop picks the digit; inner loop repeats it $rows - $i + 1 times.

PHP
<?php
$rows = 5;

for ($i = $rows; $i >= 1; $i--) {
    for ($j = $rows; $j >= $i; $j--) {
        echo $i;
    }
    echo PHP_EOL;
}
?>

How It Works

1. Count down. for ($i = $rows; $i >= 1; $i--) yields 5, 4, 3, 2, 1 — the digit for each row.

2. Grow repeats. When $i = 5, the inner loop runs once (5); when $i = 1, it runs five times (11111).

3. Newline. echo PHP_EOL; after the inner loop starts the next longer row of a smaller digit.

Example 2 — User Input

Read the row count from the CLI. Prefer is_numeric in real apps (shown in the tip below).

PHP
<?php
echo "Enter the number of rows: ";
$rows = (int) trim(fgets(STDIN));

for ($i = $rows; $i >= 1; $i--) {
    for ($j = $rows; $j >= $i; $j--) {
        echo $i;
    }
    echo PHP_EOL;
}
?>

How It Works

1. Read rows. Ask for a row count, then trim(fgets(STDIN)) and cast to int.

2. Same nested loops. Four rows start at 4 and end at 1111.

3. Safer input tip. Bare (int) casts turn letters into 0. Prefer:

Safer input
echo "Enter the number of rows: ";
$input = trim(fgets(STDIN));
if (!is_numeric($input) || (int) $input < 1) {
    echo "Enter a positive whole number." . PHP_EOL;
    exit(1);
}
$rows = (int) $input;

Example 3 — str_repeat Shortcut

Same shape with one call per row — best once the $rows - $i + 1 count is clear.

PHP
<?php
$rows = 5;

for ($i = $rows; $i >= 1; $i--) {
    echo str_repeat((string) $i, $rows - $i + 1) . PHP_EOL;
}
?>

How It Works

1. Count still matters. $rows - $i + 1 is the same repeat length the inner loop used.

2. Same shape. Identical output to Example 1 — keep the nested-loop version for exams that expect two loops.

3. Cast to string. str_repeat needs a string — (string) $i keeps the digit clear.

Edge Cases & Pitfalls

Check these before calling the solution done.

wrong twin

for ($i = 1; $i <= $rows; $i++) with echo $i × $i

That is Program 9 (1, 22, 333). Keep counting down and growing repeats for this pattern.

PHP_EOL inside

echo PHP_EOL inside the inner loop

That puts each digit on its own line. Print repeats without a newline; call echo PHP_EOL only after the row finishes.

wrong count

$j <= $i instead of $j >= $i

The inner bound must be for ($j = $rows; $j >= $i; $j--) so repeat count equals $rows - $i + 1.

rows = 1

Single digit

Output is just 1 — a good sanity check.

rows ≤ 0

Empty output

The outer loop never runs. Validate and prompt again for clearer UX.

multi-digit

$rows > 9

echo 10 prints two characters. Labs usually stick to 1–9 for a clean single-digit look.

Analysis

Time and Space Complexity

ProgramTimeExtra space
Nested loops (Examples 1–2)O(n²)O(1)
str_repeat shortcut (Example 3)O(n²)O(1) beyond the row string

There are n rows printing 1+2+…+n digits, so total work is n(n+1)/2.

Remember

Key Takeaways

  • Rule: for $i = n..1, print digit $i exactly n - i + 1 times.
  • Inner bound: $j from $rows down to $i grows the repeat count as the digit shrinks.
  • echo vs PHP_EOL: repeats stay on the line; echo PHP_EOL advances after each row.
  • Next step: Program 11 inverts the triangle (longest row of the top digit first).

One line: for each digit from n down to 1, print it n-i+1 times with echo, then echo PHP_EOL.

Frequently Asked Questions

The outer loop decreases i from rows down to 1. The inner loop runs j from rows down to i, so it executes once when i equals rows, twice when i is rows-1, and so on until rows times for i = 1.
for ($j = $rows; $j >= $i; $j--) runs ($rows - $i + 1) times. That count grows as i shrinks, which is why 4 prints twice, 3 prints three times, and 1 prints rows times.
echo stays on the same line. echo PHP_EOL ends the current line. Repeated digits use echo $i; the row break uses echo PHP_EOL after the inner loop.
Program 9 grows upward: row i repeats digit i exactly i times (1, 22, 333). Program 10 starts with one copy of the top digit and increases repeats as the digit decreases (5, 44, 333, 2222, 11111).
O(n²) where n is the number of rows. Total echo calls equal 1+2+…+n = n(n+1)/2.
Yes. echo str_repeat((string)$i, $rows - $i + 1) . PHP_EOL prints a full row in one call. Nested loops are better for learning; str_repeat is a handy shortcut once the bounds make sense.
Use trim(fgets(STDIN)) and check is_numeric($input) before casting to int so bad input does not produce unexpected results.
The outer loop never runs, so nothing is printed. Validate and prompt again if you want a clear user message.

Did you know?

Row digit i repeats rows - i + 1 times. The outer loop counts down from rows, so the first row shows one copy of the top digit and the last row repeats 1 for rows times — still O(n²) total prints.

Next: Inverted Repeating Triangle

Continue with the longest row of the top digit first.

Program 11 tutorial →

About the author

Mari Selvan M P
Mari Selvan M P 🔗

Developer, cloud engineer, and technical writer

  • Experience 12 years building web and cloud systems
  • Focus Full Stack Development, AWS, and Developer Education

I write practical tutorials so students and working developers can learn by doing—from databases and APIs to deployment on AWS.

AWS Certified Developer – Associate (Credly)

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PHP Number Pattern 9 — Repeating Triangle PHP Number Pattern 11 — Inverted Repeating Triangle