Number Pattern 33 in PHP

Beginner
⏱️ 5 min read
📚 Updated: Aug 2025
🎯 2 Code Examples
Nested Loops
PHP Number Pattern 33 output (1, 2 3, 3 4 5, 4 5 6 7, 5 6 7 8 9)

What You’ll Learn

How to print Number Pattern 33 in PHP using nested loops. Row $i prints $i numbers, and each number is computed using $i + $j - 1.

This is a neat pattern for practicing how row/column indices translate into printed values.

⭐ Pattern Output

For $rows = 5, the pattern looks like this:

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

Complete PHP Program

The outer loop controls the row. The inner loop prints the value $i + $j - 1 for each column position $j.

PHP
<?php
$rows = 5;

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

🧠 How It Works

1

Choose the row count

$rows = 5; sets how many lines will be printed.

Setup
2

Outer loop (rows 1..$rows)

for ($i = 1; $i <= $rows; $i++) controls which row is being printed.

Row control
3

Inner loop (columns 1..$i)

for ($j = 1; $j <= $i; $j++) prints $i numbers on the current row.

Column control
4

Compute and print $i + $j - 1

echo ($i + $j - 1) . " "; makes the row start at $i and increase by 1 across columns.

Value formula
=

Growing number triangle

Total printed values are 1+2+…+n = n(n+1)/2, so time complexity is O(n²) for n 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) {
    exit("Rows must be at least 1." . PHP_EOL);
}

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

💡 Tips for Enhancement

Try These

  • Validate input (reject $rows < 1) before printing the pattern
  • Start from 0 by using ($i + $j - 2) instead of ($i + $j - 1)
  • Align rows by printing leading spaces before each row
  • Remove the trailing space by building each row as a string and trimming it
  • Turn it into a pyramid by printing centered spacing

Avoid

  • Forgetting to move to the next line after each row (PHP_EOL)
  • Using negative or zero rows without validation
  • Mixing row/column responsibilities (outer loop = rows, inner loop = columns)
  • Assuming user input is always valid in CLI programs

Key Takeaways

1

The outer loop prints rows from 1 to $rows.

2

Row $i prints $i numbers (inner loop runs 1..$i).

3

Each value is computed using $i + $j - 1, so rows start at their index.

4

Total printed values are n(n+1)/2, giving O(n²) runtime.

❓ Frequently Asked Questions

For row $i = 2, the inner loop prints $i + $j - 1. When $j=1, it prints 2; when $j=2, it prints 3.
Because when $j = 1, the expression becomes $i + 1 - 1 = $i.
Adjust the formula. For example, ($i + $j) will shift everything up by 1, and ($i + $j - 2) will shift everything down by 1.
O(n²) for n rows because the program prints 1+2+…+n values, which equals n(n+1)/2.

Explore More PHP Number Patterns!

Practice nested loops with progressively richer number patterns and variations.

All Number Patterns →
Did you know?

If you view the values as a grid, each cell increases by 1 as you move right because $j increases by 1 in the formula $i + $j - 1.

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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