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PHP | check if a number is Even or Odd

  • Last Updated : 31 Jul, 2021

A number is called even if the number is divisible by 2 and is called odd if it is not divisible by 2. Given a number, we need to check whether it is odd or even in PHP.

Examples :

Input : 42
Output : Even
Explanation: The number 42 is divisible by 2

Input : 39
Output : Odd
Explanation: The number 39 is not divisible by 2

We can solve this problem in two different ways as described below:

  1. Using modulo (%) operator: This is the simplest method of checking for even and odd and in this method, we simply check whether the number is divisible by 2 or not using the modulo ‘%’ operator.



    Below program explains the above approach:

    PHP




    <?php
    // PHP code to check whether the number 
    // is Even or Odd in Normal way
    function check($number){
        if($number % 2 == 0){
            echo "Even"
        }
        else{
            echo "Odd";
        }
    }
      
    // Driver Code
    $number = 39;
    check($number)
    ?>


    Output :
    Odd
    

    Time Complexity: O(1)

  2. Recursive method: In the recursive approach, we reduce the number by 2 in each recursive call. If the final number is 0 then its even or else it is 1, the result will be odd.
    Below is the implementation of above approach:

    PHP




    <?php
    // Recursive function to check whether
    // the number is Even or Odd 
    function check($number){
        if($number == 0)
            return 1;
        else if($number == 1)
            return 0;
        else if($number<0)
            return check(-$number);
        else
            return check($number-2);        
    }
      
    // Driver Code
    $number = 39;
    if(check($number))
        echo "Even";
    else
        echo "Odd";
    ?>


    Output :
    Odd
    

    Time Complexity: O(n)

  3. Using Bit Manipulation:
    In this method we will find bit-wise AND of the number with 1. If the bit-wise AND is 1, then the number is odd, else even.

    Below is the implementation of above idea.

    PHP




    <?php
    // PHP code to check whether the number 
    // is Even or Odd using Bitwise Operator
    function check($number)
    {
          
        // One
        $one = 1;
          
        // Bitwise AND
        $bitwiseAnd = $number & $one;
          
        if($bitwiseAnd == 1)
        {
            echo "Odd"
        }
        else{
            echo "Even";
        }
    }
      
    // Driver Code
    $number = 39;
    check($number)
    ?>


    Output :
    Odd
    

    Time Complexity: O(1)

PHP is a server-side scripting language designed specifically for web development. You can learn PHP from the ground up by following this PHP Tutorial and PHP Examples.

Attention reader! Don’t stop learning now. Join the First-Step-to-DSA Course for Class 9 to 12 students , specifically designed to introduce data structures and algorithms to the class 9 to 12 students




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