php解码或解析每个十六进制的半字节

Question

我们如何解码php中的十六进制值？

我有十六进制值，它编码了一些数据。

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

我该如何解析每个半字节？

Answer 1

您可以提取直接从字符串中的每个蚕食它这样比较：

$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"; 
} 

您也可以解释字符串作为一个数字，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"; 
}