php - php解码或解析十六进制的每个半字节

Question

我们如何解码 php 中的十六进制值？

我有对一些数据进行编码的十六进制值。

例如：我的十六进制值 = 0x 1121 0031 在这里，这个十六进制值的每个半字节告诉我第一个半字节 1 表示 product_1 和 2 表示 product_2。对于第二个半字节，1 表示新产品，2 表示旧产品。

我怎样才能解析每个半字节？

Answer 1

您可以直接从字符串中提取每个半字节并像这样进行比较：

$data = '0x 1121 0031';
$data = substr($data, 2); //remove the 0x prefix from the string
$data = str_replace(' ', '', $data); //remove the spaces from the string
//$data is now '11210031'
echo 'the product number is ' . $data[0] . "\n";
if ($data[1] == 1) {
    echo "this is a new product\n";
} else if ($data[1] == 2) {
    echo "this is a used product\n";
}

您还可以将字符串解释为数字，然后提取位：

$data = '0x 1121 0031';
$data = substr($data, 2); //remove the 0x prefix from the string
$data = str_replace(' ', '', $data); //remove the spaces from the string
//$data is now '11210031'
$number = hexdec($data); //convert the hexadecimal number to an integer
//$number is now 0x11210031 (hexadecimal) = 287375409 (decimal)
$nibble1 = ($number >> 28) & 0xF; //shift the number right by 28 bits (each nibble is 4 bits) and select only the last 4 bits (0xF selects all bits in the last nibble)
echo "the product number is $nibble1\n";
$nibble2 = ($number >> 24) & 0xF;
if ($nibble2 == 1) {
    echo "this is a new product\n";
} else if ($nibble2 == 2) {
    echo "this is a used product\n";
}