Mirrored Number Pattern in PHP

What You’ll Learn

The mirrored number pattern prints 1 1, 12 21, 123 321, 1234 4321, 1234554321 — a natural step after the 0-centered mirror in Program 28. This tutorial covers fixed-width loops, space alignment, conditional printing, a live preview, worked PHP examples, edge cases, and complexity.

📝 Problem & Approach

Given rows = 5, print a mirrored pattern: for each i, print digits or spaces in a fixed-width left loop, then digits or spaces in a fixed-width right loop.

// rows = 5 (conceptual shape)
// 1        1
// 12      21
// 123    321
// 1234  4321
// 1234554321

Inputs & Outputs

Minimal workflow

for i from 1 to rows:
    for j from 1 to rows:
        if j <= i: print j
        else: print space
    for k from rows down to 1:
        if k > i: print space
        else: print k
    print newline

Approach comparison

🔮 Live Preview

Choose a row count between 3 and 9 and draw the spaced mirror pattern in the browser.

Press "Draw pattern".

Examples Gallery

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

<?php
for ($i = 1; $i <= 5; $i++) {
    for ($j = 1; $j <= 5; $j++) {
        if ($j <= $i) {
            echo $j;
        } else {
            echo " ";
        }
    }

    for ($k = 5; $k >= 1; $k--) {
        if ($k > $i) {
            echo " ";
        } else {
            echo $k;
        }
    }

    echo PHP_EOL;
}

1        1
12      21
123    321
1234  4321
1234554321

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

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

    for ($k = $rows; $k >= 1; $k--) {
        echo ($k > $i) ? " " : $k;
    }

    echo PHP_EOL;
}

Enter rows: 4
1      1
12    21
123  321
12344321

<?php
$rows = 3;

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

    for ($k = $rows; $k >= 1; $k--) {
        if ($k > $i) {
            echo " ";
        } else {
            echo $k;
        }
    }

    echo PHP_EOL;
}

1    1
12 21
123321

🔎 Worked Walkthrough — rows = 5

Trace each outer-loop value of i, what the left and right loops print, and the full row output.

Gap spaces = 2 * (rows - i) between the left and right digit groups — zero when i = rows.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

💡 Best Practices