How to Check if a Number is Odd or Even in PHP

  1. Using a PHP Expression
  2. Simple Bit Checking: the fastest way
  3. About Odd and Even Numbers

This is a short guideline on how to check whether a number is odd or even in PHP. It is handy, especially when it is necessary to find a solution for alternative colors on table rows of HTML.

Using a PHP Expression

The expression below is used for checking if a number is odd, even, or false:

$number % 2 == 0

This expression can operate on any integer value and Arithmetic Operations. An example is demonstrated below:

$number = 20; 
if ($number % 2 == 0) { 
   print "It's even"; 
}

The output of this example will look like this:

It's even

Simple Bit Checking: the fastest way

The fastest and shortest way to check whether a number is odd or even is the simple bit checking like this:

n & 1

Here is an example:

if ( $num & 1 ) { 
   //odd 
} else { 
   //even 
}

About Odd and Even Numbers

Here, you will find the explanation of odd and even numbers. Even number is considered a number, which is a multiple of two. When it is divided by two, it will not leave a remainder.

On the contrary, the Odd number will leave a remainder once it is divided by two. An odd number is not considered a multiple of two.

For a better perception, let’s consider an example.

In the case of dividing 2 into 5, 2 and a remainder of 1 will be left. Here, we can conclude that 5 is an odd number.

In the case of dividing 2 into 4, 2 and no remainder will be left. So, 4 is considered an even number.


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