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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 below example, 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. Please 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.



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