Repeated Number Triangle Pattern in PHP

What You’ll Learn

The repeated number triangle prints 1, 22, 333, 4444, 55555 — row $i repeats digit $i exactly $i times. This tutorial covers nested-loop logic, live preview, worked PHP examples, edge cases, and O(n²) complexity.

📝 Problem & Approach

Given a positive integer $rows (e.g. 5), print a repeated number triangle: row $i repeats digit $i exactly $i times (e.g. row 3 → 333).

// $rows = 5 (conceptual shape)
for ($i = 1; $i <= $rows; $i++) {
    for ($j = 1; $j <= $i; $j++) {
        echo $i;          // digit i, repeated i times
    }
    echo PHP_EOL;         // next row
}

Inputs & Outputs

Minimal workflow

for i from 1 to rows:
    for j from 1 up to i:
        print i
    print newline

Approach comparison

🔮 Live Preview

Enter a row count and draw the repeated number triangle in the browser.

Press "Draw pattern".

Examples Gallery

Three complete PHP programs — fixed $rows = 5, fgets(STDIN) input, and a spaced-output variant. Click View Output to reveal sample console results.

<?php
$rows = 5;

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

1
22
333
4444
55555

<?php
echo "Enter the number of rows: ";
$input = trim(fgets(STDIN));
if (!is_numeric($input)) {
    echo "Invalid input." . PHP_EOL;
    exit(1);
}
$rows = (int) $input;

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

Enter the number of rows: 4
1
22
333
4444

<?php
$rows = 5;

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

1
2 2
3 3 3
4 4 4 4
5 5 5 5 5

🔎 Worked Walkthrough — row $i = 3 (when $rows = 5)

Trace how increasing $i adds one more copy of the row digit.

After the inner loop, echo PHP_EOL moves to the next row.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices