php解码或解析十六进制的每个半字节

How can we decode a hex value in php?

I have hex value which encodes some data.

for ex: my hex value = 0x 1121 0031 here, each nibble of this hex value tells me something like first nibble 1 means product_1 and 2 for product_2. and for the second nibble 1 means new product, 2 means old product.

how can I parse each nibble?

You can extract each nibble directly from the string and compare it like this:

$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 ' . $data[0] . "
";
if ($data[1] == 1) {
    echo "this is a new product
";
} else if ($data[1] == 2) {
    echo "this is a used product
";
}

You can also interpret the string as a number and then extract the bits:

$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
";
$nibble2 = ($number >> 24) & 0xF;
if ($nibble2 == 1) {
    echo "this is a new product
";
} else if ($nibble2 == 2) {
    echo "this is a used product
";
}