PHP | check if a number is Even or Odd

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:
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:PHPPHP<?php// PHP code to check whether the number // is Even or Odd in Normal wayfunction check($number){    if($number % 2 == 0){        echo "Even";     }    else{        echo "Odd";    }}  // Driver Code$number = 39;check($number)?>Output :Odd
Time Complexity: O(1)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:PHPPHP<?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)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.PHPPHP<?php// PHP code to check whether the number // is Even or Odd using Bitwise Operatorfunction 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)
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:PHPPHP<?php// PHP code to check whether the number // is Even or Odd in Normal wayfunction check($number){    if($number % 2 == 0){        echo "Even";     }    else{        echo "Odd";    }}  // Driver Code$number = 39;check($number)?>Output :Odd
Time Complexity: O(1)
Below program explains the above approach:
PHP
<?php// PHP code to check whether the number // is Even or Odd in Normal wayfunction check($number){    if($number % 2 == 0){        echo "Even";     }    else{        echo "Odd";    }}  // Driver Code$number = 39;check($number)?>
Odd

Time Complexity: O(1)
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:PHPPHP<?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)
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";?>
Odd

Time Complexity: O(n)
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.PHPPHP<?php// PHP code to check whether the number // is Even or Odd using Bitwise Operatorfunction 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)
Below is the implementation of above idea.
PHP
<?php// PHP code to check whether the number // is Even or Odd using Bitwise Operatorfunction check($number){          // One    $one = 1;          // Bitwise AND    $bitwiseAnd = $number & $one;          if($bitwiseAnd == 1)    {        echo "Odd";     }    else{        echo "Even";    }}  // Driver Code$number = 39;check($number)?>
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.
ShivamKD
PHP-basics
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