Increasing Number Triangle Starting from 0 in PHP

What You’ll Learn

The increasing number triangle using $i + $j prints 0, 1 2, 2 3 4, … — a natural follow-up after Program 33’s $i + $j - 1 triangle starting from 1. This tutorial covers the $i + $j formula, nested loops, a live preview, worked PHP examples, edge cases, and complexity.

📝 Problem & Approach

Given $max = 5, print a zero-based left-shifted increasing triangle: for each row $i, print $j = 0..$i values of $i + $j separated by spaces.

// $max = 5 ($i runs 0..5)
// 0
// 1 2
// 2 3 4
// 3 4 5 6
// 4 5 6 7 8
// 5 6 7 8 9 10

Inputs & Outputs

Minimal workflow

for i from 0 to max:
    for j from 0 to i:
        print (i + j) + space
    print newline

Approach comparison

🔮 Live Preview

Choose a max i value between 2 and 9 and draw the increasing triangle in the browser.

Press "Draw pattern".

Examples Gallery

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

<?php
for ($i = 0; $i <= 5; $i++) {
    for ($j = 0; $j <= $i; $j++) {
        echo ($i + $j) . " ";
    }
    echo PHP_EOL;
}

0
1 2
2 3 4
3 4 5 6
4 5 6 7 8
5 6 7 8 9 10

<?php
echo "Enter max i: ";
$max = (int) trim(fgets(STDIN));
if ($max < 0) return;

for ($i = 0; $i <= $max; $i++) {
    for ($j = 0; $j <= $i; $j++) {
        echo ($i + $j) . " ";
    }
    echo PHP_EOL;
}

Enter max i: 2
0
1 2
2 3 4

<?php
$max = 2;

for ($i = 0; $i <= $max; $i++) {
    for ($j = 0; $j <= $i; $j++) {
        echo ($i + $j) . " ";
    }
    echo PHP_EOL;
}

0
1 2
2 3 4

🔎 Worked Walkthrough — $max = 5

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

Prints per row = $i + 1 — total prints = ($max+1)($max+2)/2 when $i runs 0..$max.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices