PHP按位操作不返回正確的值

Question

我有一個函數，它接受一個數字並返回與天數對應的數組（該數字將在一週中的每一天被屏蔽）。但是，數組將返回特定值的所有日期，併爲另一個值返回一個空數組。 下面是功能

function get_days($days) { 
    $days_arr = array(); 


echo "days: " . decbin($days) . " - type: " . gettype($days) . "<br/>"; 
echo "type1: " . gettype($days & 0x01) . " - type2: " . gettype(0x01) . "<br/>"; 
echo "days & 0x01 = " . dechex($days & 0x01) . " = " . ($days & 0x01 == 0x01) . "<br/>"; 
echo "days & 0x02 = " . dechex($days & 0x02) . " = " . ($days & 0x02 == 0x02) . "<br/>"; 
echo "days & 0x04 = " . dechex($days & 0x04) . " = " . ($days & 0x04 == 0x04) . "<br/>"; 
echo "days & 0x08 = " . dechex($days & 0x08) . " = " . ($days & 0x08 == 0x08) . "<br/>"; 
echo "days & 0x10 = " . dechex($days & 0x10) . " = " . ($days & 0x10 == 0x10) . "<br/>"; 


    if($days & 0x01 == 0x01) 
     $days_arr[] = 'M'; 

    if($days & 0x02 == 0x02) 
     $days_arr[] = 'T'; 

    if($days & 0x04 == 0x04) 
     $days_arr[] = 'W'; 

    if($days & 0x08 == 0x08) 
     $days_arr[] = 'H'; 

    if($days & 0x10 == 0x10) 
     $days_arr[] = 'F'; 

    return $days_arr; 
} 

下面是回聲

days: 10101 - type: integer 
type1: integer - type2: integer 
days & 0x01 = 1 = 1 
days & 0x02 = 0 = 1 
days & 0x04 = 4 = 1 
days & 0x08 = 0 = 1 
days & 0x10 = 10 = 1 
days: 1010 - type: integer 
type1: integer - type2: integer 
days & 0x01 = 0 = 0 
days & 0x02 = 2 = 0 
days & 0x04 = 0 = 0 
days & 0x08 = 8 = 0 
days & 0x10 = 0 = 0 

我似乎無法弄清楚這個問題背後的原因的結果，這似乎是合乎邏輯，我認爲這應該工作。

Answer 1

這是一個運算符優先級問題。請參閱：

http://php.net/manual/en/language.operators.precedence.php

所以==高於&。你不應該做的事：

$days & 0x02 == 0x02 

但是：

($days & 0x02) == 0x02