Continuous Number Triangle in PHP

Beginner
⏱️ 6 min read
📚 Updated: Aug 2025
🎯 2 Code Examples
Counters
Continuous number triangle output in PHP (1, 2 3, 4 5 6, 7 8 9 10)

What You’ll Learn

How to print a continuous number triangle in PHP where numbers keep increasing across rows: 1, 2 3, 4 5 6, 7 8 9 10.

We’ll use a counter variable that increments after every print, plus nested loops to control rows and columns.

⭐ Pattern Output

For $rows = 4, the pattern looks like this:

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

Complete PHP Program

The counter $k starts at 1 and increments on every print, so the sequence continues across rows.

PHP
<?php
$rows = 4;
$k = 1;

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

🧠 How It Works

1

Initialize the counter

$k = 1; holds the next number to print.

Setup
2

Outer loop (rows)

for ($i = 1; $i <= $rows; $i++) decides how many values each row prints.

Row control
3

Inner loop (print and increment)

Each iteration prints $k and then increments it using $k++, so the next print uses the next integer.

Counting
4

New line per row

echo PHP_EOL; moves to the next row.

Line break
=

Continuous sequence

Because the counter is not reset, numbers continue increasing across rows.

2

Variation — User Input (CLI) Version

Let the user decide the number of rows at runtime using standard input (run from terminal with php):

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

if ($rows < 1) {
    echo "Please enter a positive number." . PHP_EOL;
    exit(1);
}

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

💡 Tips for Enhancement

Try These

  • Start from a custom value by setting $k = 10 (or asking the user)
  • Remove trailing spaces by joining an array of row values
  • Print a Floyd’s triangle variant by changing row count and formatting
  • Right-align the triangle using leading spaces
  • Use sprintf padding to align multi-digit numbers in columns

Avoid

  • Resetting the counter inside the outer loop (that would restart each row)
  • Forgetting the newline after each row
  • Skipping input validation for CLI mode
  • Assuming single-digit numbers (formatting matters for larger triangles)

Key Takeaways

1

A single counter outside the loops keeps numbers continuous across rows.

2

The outer loop controls how many values appear per row (1, 2, 3, ...).

3

Total numbers printed for r rows is r(r+1)/2.

4

Formatting becomes important once numbers grow beyond single digits.

❓ Frequently Asked Questions

Yes—this is essentially Floyd’s triangle: consecutive numbers arranged in a triangular form.
Because $k is initialized once and incremented on every print; it is not reset inside the outer loop.
Use padded printing like printf("%3d ", $k++); to keep columns aligned.
O(r²) for r rows, since total prints grow as \(r(r+1)/2\).

Explore More PHP Number Patterns!

Continuous counters are a core pattern in loop problems—try combining them with conditions and alignment.

All Number Patterns →
Did you know?

The triangular number formula \(r(r+1)/2\) tells you exactly how many values are printed for r rows—handy for estimating runtime and output size.

About the author

Mari Selvan M P
Mari Selvan M P 🔗

Developer, cloud engineer, and technical writer

  • Experience 12 years building web and cloud systems
  • Focus Full Stack Development, AWS, and Developer Education

I write practical tutorials so students and working developers can learn by doing—from databases and APIs to deployment on AWS.

AWS Certified Developer – Associate (Credly)

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