0-Centered Mirror Numbers in PHP

Beginner
⏱️ 7 min read
📚 Updated: Aug 2025
🎯 2 Code Examples
Nested Loops
0-centered mirror number pattern output in PHP (0, 909, 89098, ..., 1234567890987654321)

What You’ll Learn

How to print a 0-centered mirror number pattern in PHP where each row mirrors around a central 0.

Example last line: 1234567890987654321.

This pattern is built using two inner loops: one ascending to 9, one descending back to the start, with a fixed 0 in the middle.

⭐ Pattern Output

The pattern looks like this:

Output
0
909
89098
7890987
678909876
56789098765
4567890987654
345678909876543
23456789098765432
1234567890987654321
1

Complete PHP Program

We print digits from $i up to 9, then print 0, then print digits from 9 down to $i.

PHP
<?php
for ($i = 10; $i >= 1; $i--) {
    for ($j = $i; $j < 10; $j++) {
        echo $j;
    }
    echo "0";
    for ($k = 9; $k >= $i; $k--) {
        echo $k;
    }
    echo PHP_EOL;
}

🧠 How It Works

1

Outer loop controls the start digit

for ($i = 10; $i >= 1; $i--) sets the leftmost digit of the row (from none down to 1).

Row control
2

Left side: print i..9

for ($j = $i; $j < 10; $j++) prints ascending digits that end at 9.

Ascending
3

Center: print 0

echo "0"; places the center digit for symmetry.

Center
4

Right side: print 9..i

for ($k = 9; $k >= $i; $k--) prints the descending mirror back to the start digit.

Descending
=

0-centered mirroring

Each row is symmetric around 0 because the right side mirrors the left side in reverse.

2

Variation — User Input (CLI) Version

Let the user choose the maximum digit (run from terminal with php):

PHP
<?php
echo "Enter the maximum digit (1-9, e.g., 9): ";
$max = (int) trim(fgets(STDIN));

if ($max < 1) {
    echo "Please enter a positive number." . PHP_EOL;
    exit(1);
}
if ($max > 9) $max = 9;

for ($i = $max + 1; $i >= 1; $i--) {
    for ($j = $i; $j <= $max; $j++) {
        echo $j;
    }
    echo "0";
    for ($k = $max; $k >= $i; $k--) {
        echo $k;
    }
    echo PHP_EOL;
}

💡 Tips for Enhancement

Try These

  • Print spaces between digits to make long lines more readable
  • Replace the center 0 with another symbol to create new variants
  • Use padding to align multi-digit output if you increase beyond single digits
  • Generate only a subset of rows by limiting the outer loop range
  • Convert it into a diamond by adding a second half that shrinks again

Avoid

  • Mixing loop bounds (ascending must stop at max, descending must start at max)
  • Forgetting the newline after each row
  • Skipping input validation for the CLI version
  • Assuming the first inner loop always prints at least one number

Key Takeaways

1

Each row prints an ascending part, a center 0, then a descending mirror.

2

The start digit changes each row via the outer loop.

3

Mirroring is achieved by reversing the loop direction for the right side.

4

Parameterize the max digit to generate smaller or larger versions.

❓ Frequently Asked Questions

Because the row start is above 9, so the ascending and descending loops don’t print any digits—only the center 0 appears.
Yes—replace echo "0"; with any character or number you like.
Change the echo statements to include a space, like echo $j . " "; and echo $k . " ";.
O(n²) for n rows, since each row prints O(n) digits across multiple loops.

Explore More PHP Number Patterns!

Mirror patterns like this build strong intuition for symmetric loops and string building.

All Number Patterns →
Did you know?

Symmetry often comes from printing a sequence forward and then printing it backward—exactly what we do here around the center 0.

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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