比如某个type 字段，存储可以选择，原创，搞笑，人物，好看等来存储，相当于页面的选择是选项多选。

这时候，可以使用按位来存储。

class Bit{


//begin
public static function setBit($index, $bitValue){
    $bitValue = $bitValue | (1 << $index);
    return $bitValue;
}

public static function setBits(array $indexList, $bitValue){
    $mask = 0;
    foreach ($indexList as $index) {
        $mask = $mask | (1 << $index);
    }
}

$bitValue = self::setBitsByMask($mask, $bitValue);
    return $bitValue;
}

public static function setBitsByMask($mask, $bitValue){
    $bitValue = $bitValue | $mask;
    return $bitValue;
}

public static function unsetBit($index, $bitValue){
    $bitValue = $bitValue & ~(1 << $index);
    return $bitValue;
}

public static function unsetBits(array $indexList, $bitValue){
    $mask = 0;
    foreach ($indexList as $index) {
        $mask = $mask | (1 << $index);
    }

    $bitValue = self::unsetBitsByMask($mask, $bitValue);
    return $bitValue;
}

public static function unsetBitsByMask($mask, $bitValue) {
    $bitValue = $bitValue & ~$mask;
    return $bitValue;
}

public static function getArray ($bitValue, $keyArr = array(), $keyName = array()) {
    $output = [];
    $bitArr = array_reverse(str_split(base_convert($bitValue, 10, 2)));

    if(!empty($keyArr)) {
        $tmp = [];
        foreach ($keyArr as $key) {
            $tmp[$key] = isset($bitArr[$key]) ? (int) $bitArr[$key] : 0;
        }
        $bitArr = $tmp;
    }

    if(empty($keyName)) return $bitArr;

    foreach ($bitArr as $k=>$val) {

        if($val && isset($keyName[$k])) {
            $output[] = $keyName[$k];
        }
    }

    return $output;
}

public static function isBitSet($index, $bitValue){
    return (bool) ($bitValue & (1 << $index));
}

}

class UseBit{


const BIT_0 = 0;
const BIT_1 = 1;
const BIT_2 = 2;
const BIT_3 = 3;
const BIT_4 = 4;

//你要操作的数组
public static $BitArr = [
self::BIT_0 =>'a',
self::BIT_1 =>'b',
self::BIT_2 =>'c',
self::BIT_3 =>'d',
self::BIT_4 =>'e'
];

public static function testSet(){
    $post = [0,2,3];
    $mask = 0;

    $keys = array_keys(self::$BitArr);
    foreach ($post as $key) {
        if(in_array($key, $keys)){
    $mask = Bit::setBit($key, $mask);
    }
}
echo $mask;
$a = [2,3,4];
$b = [
'a'=>8,
'b'=>7,
'c'=>6,
];
$a = array_reverse($a);
$b = array_reverse($b);
var_dump($a);
var_dump($b);
}



}

UseBit::testSet()."set\n";