Reverse Repeating-Letter Alphabet Triangle in PHP
What You'll Learn
This program prints a triangle where each row repeats a single letter, but letters go backward: E, DD, CCC, BBBB, AAAAA.
It’s the mirror of Program 9 (A, BB, CCC, ...).
⭐ Pattern Output
For rows = 5:
E
DD
CCC
BBBB
AAAAAComplete PHP Program
Fixed rows = 5 version (nested loops):
<?php
$rows = 5;
$alpha = range('A', 'Z');
for ($i = $rows - 1; $i >= 0; $i--) {
for ($j = $rows - 1; $j >= $i; $j--) {
echo $alpha[$i];
}
echo PHP_EOL;
}🧠 How It Works
Alphabet array
$alpha = range('A', 'Z'); lets you access letters by index (0=>A, 1=>B, ...).
Outer loop walks backward
$i goes from $rows - 1 down to 0, selecting E, D, C, B, A for 5 rows.
Inner loop repeats the chosen letter
The inner loop runs from $rows - 1 down to $i, producing 1, 2, 3, 4, 5 repeats as $i decreases.
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.
Put it together
The outer loop controls rows, the inner loops control what prints on each row, and PHP_EOL separates the lines.
Variation — User Input (CLI) Version
Reads rows from standard input and clamps to a max of 26:
<?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 = $rows - 1; $i >= 0; $i--) {
for ($j = $rows - 1; $j >= $i; $j--) {
echo $alpha[$i];
}
echo PHP_EOL;
}💡 Tips for Enhancement
Try These
- Compare with Program 9 (forward letters)
- Use
str_repeat($alpha[$i], $rows - $i)to avoid the inner loop - Switch to lowercase using
range('a', 'z') - Center-align by printing leading spaces
Avoid
- Allowing
$rows> 26 without handling the alphabet size - Using
<br>in CLI examples (usePHP_EOL) - Changing the letter inside the inner loop if you want solid rows
Key Takeaways
The outer loop selects the row letter from E down to A (for 5 rows).
The inner loop repeats that letter, growing the row length.
Total characters printed is \(n(n+1)/2\), so runtime is O(n²).
❓ Frequently Asked Questions
$i = 2 (0-based), the selected letter is $alpha[2] which is C. The inner loop runs three times, so you get CCC.$rows so that $rows - 1 maps to your top letter (e.g., 4 rows start from D).Next: PHP Alphabet Pattern 11
Continue to the next program for another alphabet pattern in PHP.
You can compute the row letter without an array: chr(ord('A') + $i). For reverse order you can use chr(ord('A') + ($rows - 1 - $i)).
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