Test if number is odd or even

You were right in thinking mod was a good place to start. Here is an expression which will return true if $number is even, false if odd:

$number % 2 == 0

Works for every integer^PHP value, see as well Arithmetic Operators^PHP.

Example:

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

Output:

It's even

Another option is a simple bit checking.

n & 1

for example:

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

Yes using the mod

$even = ($num % 2 == 0);
$odd = ($num % 2 != 0);

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