Inverted Repeating Number Triangle Pattern in PHP

What You’ll Learn

The inverted repeating number triangle widens first then shrinks: digit i repeats exactly i times — nested loops, echo vs PHP_EOL, and a clear visual result. This tutorial covers the shape rule, loop structure, a live preview, algorithm steps, worked PHP examples, edge cases, and complexity.

📝 Problem & Approach

Given a positive integer rows, print an inverted repeating number triangle: row i repeats digit i exactly i times, with the outer loop counting from rows down to 1.

// First 5 rows (conceptual shape)
// 55555
// 4444
// 333
// 22
// 1

Inputs & Outputs

Minimal workflow

for i from rows down to 1:
    repeat i times:
        print i (no newline)
    print newline

Approach comparison

🔮 Live Preview

Choose a row count between 1 and 20 and draw the inverted repeating number triangle in the browser.

Press "Draw pattern".

Examples Gallery

Three complete PHP programs — fixed row count, CLI input, and a str_repeat shortcut. Click View Output to reveal sample console results.

<?php
$rows = 5;

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

55555
4444
333
22
1

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

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

Enter the number of rows: 4
4444
333
22
1

<?php
$rows = 5;

for ($i = $rows; $i >= 1; $i--) {
    echo str_repeat((string) $i, $i) . PHP_EOL;
}

55555
4444
333
22
1

🔎 Worked Walkthrough — rows = 4

Trace each outer-loop value of i and count how many times the inner loop prints digit i.

Total digit prints: 1 + 2 + 3 + 4 = 10 = 4×5/2.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices