<?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);        
}
  
// Check the number odd or even
$number = 35;
if(check($number))
    echo "Even";
else
    echo "Odd";
?>

因此，输出将是Odd

试试这个,

$number = 10;
 switch ($number%2)
 {
 case 0:
 echo "It's even";
 break;
 default:
 echo "It's odd";
 }

所有偶数除以2都得整数

$number = 4;
if(is_int($number/2))
{
   echo("Integer");
}
else
{
   echo("Not Integer");
}

两个简单的位函数，返回0表示False，返回1表示True。

# is_odd: 1 for odd , 0 for even
odd = number & 1

# is_even: 1 for even , 0 for odd
even = number & 1 ^ 1

另一种选择是简单的位检查。

n & 1

例如:

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

使用位操作: 在此方法中，您将找到带有1的数字的逐位与。如果位与为1，则该数字为奇数，否则为偶数。

function odd($var){
    return $var & 1;
}
function even($var){
    return !($var&1);
}
$arr = range(1,10);

echo "Odd Numbers: ";
echo "<pre>";
    print_r(array_filter($arr2, 'odd'));
echo "<pre>";

echo "<br>Even Numbers: ";
echo "<pre>";
    print_r(array_filter($arr2, 'even'));
echo "</pre>";

输出将是:

Odd Numbers:
Array
(
    [0] => 1
    [2] => 3
    [4] => 5
    [6] => 7
    [8] => 9
)

Even Numbers: 
Array
(
    [1] => 2
    [3] => 4
    [5] => 6
    [7] => 8
    [9] => 10
)