Shrinking Repeated Number Triangle in PHP

Beginner
⏱️ 5 min read
📚 Updated: Aug 2025
🎯 2 Code Examples
Nested Loops
Shrinking repeated number triangle output (55555, 4444, 333, 22, 1) in PHP programming

What You’ll Learn

How to print a shrinking repeated number triangle in PHP using nested for loops. Each row prints the same digit multiple times, and both the digit and repetition count decrease each row.

This pattern is a common practice problem for understanding how to shrink output using loop boundaries.

⭐ Pattern Output

For $n = 5, the pattern looks like this:

Output
55555
4444
333
22
1
1

Complete PHP Program

Fixed $n = 5 version:

PHP
<?php
$n = 5;

for ($i = $n; $i >= 1; $i--) {
    for ($j = 1; $j <= $i; $j++) {
        echo $i;
    }
    echo PHP_EOL;
}

🧠 How It Works

1

Choose the size

$n = 5; sets the starting digit and the maximum row width.

Setup
2

Outer loop (digit decreases)

for ($i = $n; $i >= 1; $i--) chooses which digit to print on the row (5, 4, 3, 2, 1).

Row control
3

Inner loop (repeat $i times)

for ($j = 1; $j <= $i; $j++) prints echo $i; exactly $i times, so the row shrinks as $i shrinks.

Repetition
4

New line

echo PHP_EOL; ends the row and moves to the next line.

Line break
=

Shrinking repeated triangle

Total prints are triangular, so the time complexity is O(n²) for n rows.

2

Variation — User Input (CLI) Version

Let the user decide $n at runtime (run from terminal with php):

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

for ($i = $n; $i >= 1; $i--) {
    for ($j = 1; $j <= $i; $j++) {
        echo $i;
    }
    echo PHP_EOL;
}

💡 Tips for Enhancement

Try These

  • Validate input (reject $n < 1) before printing
  • Add spaces between digits (for example, echo $i . " ";)
  • Reverse the outer loop direction to build a growing repeated-digit triangle
  • Use the same idea to print characters instead of digits
  • Try printing into a string per row before echoing for more control

Avoid

  • Forgetting the newline after each row
  • Using negative or zero values without validating input
  • Printing $j instead of $i (this pattern repeats the row digit)
  • Assuming CLI input is always valid (guard fgets() and casting if needed)

Key Takeaways

1

The outer loop selects the digit for each row (from $n down to 1).

2

The inner loop repeats the digit exactly $i times.

3

Total prints are triangular, so runtime is O(n²).

4

This pattern is a great building block for inverted repeated-digit triangles.

❓ Frequently Asked Questions

Because when $i = 5, the inner loop runs 5 times and prints $i each time.
Set $n to the size you want. The first row prints $n repeated $n times, and the last row prints 1.
Yes—print echo $i . " "; instead of echo $i;.
O(n²) for n rows: total prints are 1+2+…+n = n(n+1)/2.

Next: PHP Number Pattern 12

Continue to Program 12 to learn another number pattern in PHP.

Program 12 →
Did you know?

Many “triangle” patterns are just different ways of deciding what to print (value) and how many times to print it (count).

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)

12 people found this page helpful

PHP Number Pattern 10 PHP Number Pattern 12