PHP - Swap two numbers

There are two common ways to swap the value of two variables:

• Swap the value of two variables using a temporary variable
• Swap the value of two variables without using temporary variable

Method 1: Swap the value of two variables using a temporary variable

In the example below, the initial value of variables x and y are 10 and 25. A temporary variable called temp is created to store the value of x and then the value of y is assigned to x. Finally, value of temp (which stores values of x) is assigned to variable y. The final value of variables x and y after swap are 25 and 10 respectively.

<?php
function swap($x, $y) {
  echo "Before Swap.\n";
  echo "x = $x \n";
  echo "y = $y \n";

  //Swap technique
  $temp = $x;
  $x = $y;
  $y = $temp;

  echo "After Swap.\n";
  echo "x = $x \n";
  echo "y = $y \n";
}

swap(10, 25);
?>

The above code will give the following output:

Before Swap.
x = 10
y = 25
After Swap.
x = 25
y = 10

Method 2: Swap the value of two variables without using temporary variable

+ operator is used to swap the value of two variables. In this method no temporary variable is used. See the example below for syntax.

<?php
function swap($x, $y) {
  echo "Before Swap.\n";
  echo "x = $x \n";
  echo "y = $y \n";

  //Swap technique
  $x = $x + $y;
  $y = $x - $y;
  $x = $x - $y;

  echo "After Swap.\n";
  echo "x = $x \n";
  echo "y = $y \n";
}

swap(10, 25);
?>

The above code will give the following output:

Before Swap.
x = 10
y = 25
After Swap.
x = 25
y = 10

Similarly, others operators can also be used in this method. Please see the page: PHP - Swap two numbers without using Temporary Variable.