//checking even and odd
$num =14;

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

if($even){
    echo "Number is even.";
} else {
    echo "Number is odd.";
}

//checking even and odd
$num =14;

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

if($even){
    echo "Number is even.";
} else {
    echo "Number is odd.";
}

PHP自动将null和空字符串转换为0。对模也是这样。因此，代码将

$number % 2 == 0 or !($number & 1)

$number = "或$number = null 结果为true。 因此，我对它进行了更广泛的测试:

function testEven($pArg){
    if(is_int($pArg) === true){
        $p = ($pArg % 2);
        if($p === 0){
            print "The input '".$pArg."' is even.<br>";
        }else{
            print "The input '".$pArg."' is odd.<br>";
        }
    }else{
        print "The input '".$pArg."' is not a number.<br>";
    }
}

The print is there for testing purposes, hence in practice it becomes:
function testEven($pArg){
    if(is_int($pArg)=== true){
        return $pArg%2;
    }
    return false;
}

这个函数对于任何奇数返回1，对于任何偶数返回0，当它不是数字时返回false。我总是写=== true或=== false来让我自己(和其他程序员)知道测试是预期的。

我做了一些测试，发现在mod, is_int和&-操作符之间，mod是最快的，紧随其后的是&-操作符。 Is_int几乎比mod慢4倍。

I used the following code for testing purposes: $number = 13; $before = microtime(true); for ($i=0; $i<100000; $i++) { $test = ($number%2?true:false); } $after = microtime(true); echo $after-$before." seconds mod<br>"; $before = microtime(true); for ($i=0; $i<100000; $i++) { $test = (!is_int($number/2)?true:false); } $after = microtime(true); echo $after-$before." seconds is_int<br>"; $before = microtime(true); for ($i=0; $i<100000; $i++) { $test = ($number&1?true:false); } $after = microtime(true); echo $after-$before." seconds & operator<br>"; The results I got were pretty consistent. Here's a sample: 0.041879177093506 seconds mod 0.15969395637512 seconds is_int 0.044223070144653 seconds & operator

是的，使用mod

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

另一种选择是简单的位检查。

n & 1

例如:

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