Centered Palindromic Number Pyramid in PHP

Beginner
⏱️ 6 min read
📚 Updated: Aug 2025
🎯 2 Code Examples
Nested Loops
Centered palindromic number pyramid pattern output in PHP programming

What You’ll Learn

How to print a centered palindromic number pyramid in PHP using three nested loops.

You’ll combine leading spaces, ascending numbers, and descending numbers to form each row.

⭐ Pattern Output

For 5 rows, the pattern looks like this:

Output
        1
      1 2 1
    1 2 3 2 1
  1 2 3 4 3 2 1
1 2 3 4 5 4 3 2 1
1

Complete PHP Program

First print leading spaces, then ascending sequence, then descending mirror.

PHP
<?php
for ($i = 1; $i <= 5; $i++) {
    for ($j = 5; $j > $i; $j--) {
        echo "  ";
    }
    for ($k = 1; $k <= $i; $k++) {
        echo $k . " ";
    }
    $n = $k - 1;
    for ($m = 1; $m < $i; $m++) {
        echo --$n . " ";
    }
    echo PHP_EOL;
}

🧠 How It Works

1

Outer loop controls rows

for ($i = 1; $i <= 5; $i++) sets the current row size.

Row control
2

Leading spaces

for ($j = 5; $j > $i; $j--) adds indentation to center the row.

Alignment
3

Ascending then descending

Print 1..$i, then set $n = $k - 1 and print $n-1..1.

Palindrome build
4

New line per row

echo PHP_EOL; prints each palindrome on a separate line.

Line break
=

Centered palindromic pyramid

Row widths grow by 2 each line, and total loop work is O(n²).

2

Variation — User Input (CLI) Version

This version accepts row count from user input (run from terminal with php):

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

if ($n < 1) {
    echo "Rows must be at least 1" . PHP_EOL;
    exit;
}

for ($i = 1; $i <= $n; $i++) {
    for ($j = $n; $j > $i; $j--) {
        echo "  ";
    }
    for ($k = 1; $k <= $i; $k++) {
        echo $k . " ";
    }
    $temp = $k - 1;
    for ($m = 1; $m < $i; $m++) {
        echo --$temp . " ";
    }
    echo PHP_EOL;
}

💡 Tips for Enhancement

Try These

  • Swap numbers with letters to build alphabet palindromic pyramids
  • Use fixed-width formatting for clean multi-digit alignment
  • Create an inverted pyramid by reversing outer loop direction
  • Add hollow-center logic to print only boundary values
  • Parameterize spacing token for console vs web output

Avoid

  • Mixing HTML-only empty div spacing in CLI examples
  • Forgetting to reset descending counter each row
  • Using wrong descending bound and duplicating middle value
  • Skipping validation for invalid input rows

Key Takeaways

1

Three loops handle spaces, ascending values, and descending values.

2

Each row is a palindrome around its peak number.

3

Indentation controls pyramid centering.

4

Same design can be adapted to star, alphabet, and hollow pyramids.

❓ Frequently Asked Questions

It prints ascending sequence 1..3, then mirrors down 2..1.
Set $n = 7 in dynamic version; all loops adjust automatically.
Yes, but readability and centering may suffer, especially for larger values.
O(n²) because each row does work proportional to n.

Explore More PHP Number Patterns!

Continue mastering centered and mirrored patterns with nested loops.

All Number Patterns →
Did you know?

Palindromic pyramids are frequently used in programming interviews to assess loop control, indexing, and symmetry logic together.

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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