Swap Two Numbers in PHP

What You’ll Learn

Swapping exchanges two variables so each holds the other’s old value: a=5, b=10 becomes a=10, b=5. You will use a temp variable, PHP’s [$a, $b] = [$b, $a], and an optional XOR trick for integers — plus a live preview and worked examples.

📝 Problem & Approach

Given two variables, exchange their values so each holds what the other used to hold.

// Before: $a = 5,  $b = 10
// After:  $a = 10, $b = 5

Inputs & Outputs

Minimal workflow

$temp = $a
$a = $b
$b = $temp

Method comparison

🔮 Live Preview

Enter two integers and swap them with a temporary variable.

Press “Swap”.

Examples Gallery

Three complete PHP programs — temp variable, list destructuring, and XOR for integers. Click View Output to reveal sample console results.

<?php
$num1 = 5;
$num2 = 10;

echo "Before swapping: num1 = $num1, num2 = $num2\n";
$temp = $num1;
$num1 = $num2;
$num2 = $temp;
echo "After swapping: num1 = $num1, num2 = $num2\n";
?>

Before swapping: num1 = 5, num2 = 10
After swapping: num1 = 10, num2 = 5

<?php
$num1 = 5;
$num2 = 10;

echo "Before swapping: num1 = $num1, num2 = $num2\n";
[$num1, $num2] = [$num2, $num1];
echo "After swapping: num1 = $num1, num2 = $num2\n";
?>

Before swapping: num1 = 5, num2 = 10
After swapping: num1 = 10, num2 = 5

<?php
$a = 5;
$b = 10;

if ($a !== $b) {
    $a ^= $b;
    $b ^= $a;
    $a ^= $b;
}

echo "After swapping: a = $a, b = $b\n";
?>

After swapping: a = 10, b = 5

🔎 Worked Walkthrough — 5 and 10

Follow the temp variable through each assignment.

If you assign a = b first without saving, the original 5 disappears.

⚖️ Facts Worth Knowing

Handy follow-ups interviewers sometimes ask.

🎯 Practice Problems

Try these variations to lock in the pattern.

Notes

⏱️ Time and Space Complexity

Swapping two variables does a fixed number of assignments regardless of the values.

💡 Best Practices