PHP | check if a number is Even or Odd

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.