Inverted Forward Repeating Alphabet Triangle in PHP

Beginner
⏱️ 6 min read
📚 Updated: Aug 2025
🎯 2 Code Examples
Nested loops
Alphabet pattern output AAAAA, BBBB, CCC, DD, E in PHP programming

What You'll Learn

This PHP program prints an inverted repeating-letter triangle with forward letters: AAAAA, BBBB, CCC, DD, E.

Compare it with Program 11, which uses the same shrinking width but letters go backward.

⭐ Pattern Output

For rows = 5:

Output
AAAAA
BBBB
CCC
DD
E
1

Complete PHP Program

Fixed rows = 5 version:

PHP
<?php
$rows = 5;
$alpha = range('A', 'Z');

for ($i = 0; $i < $rows; $i++) {
    for ($j = $rows - 1; $j >= $i; $j--) {
        echo $alpha[$i];
    }
    echo PHP_EOL;
}

🧠 How It Works

1

Outer loop chooses the letter

$i goes from 0 to 4, selecting A, B, C, D, E.

2

Inner loop shrinks the width

The inner loop runs from $rows - 1 down to $i, so it prints 5, 4, 3, 2, 1 characters.

3

One letter per row

We print $alpha[$i] inside the inner loop, so the same row letter repeats.

4

Print the line break

After building one row, print PHP_EOL to move to the next line. This keeps the output readable in CLI output.

Newline
=

Put it together

The outer loop controls rows, the inner loops control what prints on each row, and PHP_EOL separates the lines.

2

Variation — User Input (CLI) Version

Reads rows from standard input and clamps to a max of 26:

PHP
<?php
echo "Enter the number of rows (max 26): ";
$rows = (int) trim(fgets(STDIN));
$rows = max(1, min($rows, 26));

$alpha = range('A', 'Z');

for ($i = 0; $i < $rows; $i++) {
    for ($j = $rows - 1; $j >= $i; $j--) {
        echo $alpha[$i];
    }
    echo PHP_EOL;
}

💡 Tips for Enhancement

Try These

  • Compare with Program 11 (reverse letters)
  • Use str_repeat($alpha[$i], $rows - $i) to remove the inner loop
  • Switch to lowercase using range('a', 'z')
  • Add spaces between letters for readability

Avoid

  • Allowing $rows > 26 without handling the alphabet size
  • Using <br> in CLI examples (use PHP_EOL)

Key Takeaways

1

Outer loop selects the row letter (A to E for 5 rows).

2

Inner loop prints a shrinking number of repeats (5 to 1).

3

Total printed characters is \(n(n+1)/2\), so runtime is O(n²).

❓ Frequently Asked Questions

It creates an array of uppercase letters so you can print alphabets using simple numeric indexes (0 for A, 1 for B, ...).
PHP_EOL is correct for CLI output and keeps examples consistent for terminal execution. In HTML, you would use <br> instead.
Most pattern programs print O(n) characters per row for n rows, so they are typically O(n2).

Next: PHP Alphabet Pattern 13

Continue to the next program for another alphabet pattern in PHP.

Program 13 →

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 Alphabet Pattern 11 PHP Alphabet Pattern 13