Reverse Alphabet Pattern (E to EDCBA) in PHP

Beginner
⏱️ 6 min read
📚 Updated: Aug 2025
🎯 2 Code Examples
n(n+1)/2 letters total
Reverse alphabet pattern output in PHP programming

What You'll Learn

This PHP program prints a reverse alphabet triangle where each row begins with the same ending letter (like E for 5 rows) and then prints letters backward.

For n rows, the last letter is (A + n - 1) and total printed letters are n(n + 1)/2.

⭐ Pattern Output

When you run the program with rows = 5:

Output
E
ED
EDC
EDCB
EDCBA
1

Complete PHP Program

Fixed rows = 5 version:

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

$start = $rows - 1; // 4 -> 'E'

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

🧠 How It Works

1

Create letters A to Z

$alpha = range('A', 'Z'); gives a 0-based array: $alpha[0] = 'A', $alpha[4] = 'E'.

Setup
2

Pick the starting letter

$start = $rows - 1 means for 5 rows you start at index 4, which is 'E'. For n rows you start at 'A' + (n - 1).

Start
3

Inner loop prints backward

Row $i prints indices from $start down to $start - $i, so each row is one letter longer than the previous.

Inner
=

Reverse alphabet triangle

Total printed letters are n(n + 1)/2, so time complexity is O(n²) for n rows.

2

Variation — User Input (CLI) Version

Read rows from standard input (works when you run the file from terminal using php):

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');
$start = $rows - 1;

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

💡 Tips for Enhancement

Try These

  • Print the forward pattern first (Program 1) to compare
  • Switch to lowercase using range('a', 'z')
  • Insert spaces between letters for readability
  • Make the triangle right-aligned by adding leading spaces
  • Print a continuous reverse stream by changing where you reset the start

Avoid

  • Allowing $rows > 26 without handling wrap-around
  • Using <br> in CLI examples (use PHP_EOL)
  • Off-by-one errors when computing $start - $i
  • Mixing HTML output with CLI output without intent

Key Takeaways

1

Use an alphabet array with range('A', 'Z') for clean indexing.

2

Row i prints i + 1 letters, growing the triangle by one each row.

3

Each row starts at 'A' + (rows - 1) and counts down.

4

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

❓ Frequently Asked Questions

Yes. You can compute characters with chr(ord('A') + offset). Using range('A','Z') is often simpler and avoids manual ASCII arithmetic.
That’s Program 1. Start from A and increase the end letter each row.
It’s O(n²) for n rows, because the program prints 1+2+…+n letters in total.

Next: PHP Alphabet Pattern 3

Continue to Program 3 for the next alphabet pattern in PHP.

Program 3 →
Did you know?

The trick is choosing the row start as rows - 1. Once that index is correct, the inner loop is just counting backward for a row-dependent length.

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 1 PHP Alphabet Pattern 3