Increasing Number Triangle Starting from 11 in PHP

What You’ll Learn

The increasing number triangle from 11 prints 11, 12 13, 13 14 15, … — a natural step after the number-star diamond in Program 31. This tutorial covers the 9 + $i + $j formula, nested loops, a live preview, worked PHP examples, edge cases, and complexity.

📝 Problem & Approach

Given $rows = 5, print a left-shifted increasing triangle: for each row $i, print $j = 1..$i values of 9 + $i + $j separated by spaces.

// $rows = 5 (conceptual shape)
// 11
// 12 13
// 13 14 15
// 14 15 16 17
// 15 16 17 18 19

Inputs & Outputs

Minimal workflow

for i from 1 to rows:
    for j from 1 to i:
        print (9 + $i + $j) + space
    print newline

Approach comparison

🔮 Live Preview

Choose a row count between 3 and 9 and draw the increasing triangle in the browser.

Press "Draw pattern".

Examples Gallery

Three complete PHP programs — fixed rows, custom base input, and a smaller trace demo. Click View Output to reveal sample console results.

<?php
for ($i = 1; $i <= 5; $i++) {
    for ($j = 1; $j <= $i; $j++) {
        echo (9 + $i + $j) . " ";
    }
    echo PHP_EOL;
}

11
12 13
13 14 15
14 15 16 17
15 16 17 18 19

<?php
echo "Enter rows: ";
$rows = (int) trim(fgets(STDIN));
echo "Enter base: ";
$baseVal = (int) trim(fgets(STDIN));
if ($rows < 1) return;

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

Enter rows: 3
Enter base: 9
11
12 13
13 14 15

<?php
$rows = 3;

for ($i = 1; $i <= $rows; $i++) {
    for ($j = 1; $j <= $i; $j++) {
        echo (9 + $i + $j) . " ";
    }
    echo PHP_EOL;
}

11
12 13
13 14 15

🔎 Worked Walkthrough — $rows = 5

Trace each outer-loop value of $i, inner-loop range, values printed, and full row output.

Prints per row = $i — total prints = n(n+1)/2 for n rows.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices