Why does php ip2long have negative numbers? How to deal with it?

php provides ip2long and long2ip methods for ip address processing.

1. ip2long - Convert an IPV4 string Internet protocol into a digital format

int ip2long ( string $ip_address )

Parameters: ip_address An address in a standard format.

Return value: Returns the converted number of the IP address or FALSE if ip_address is invalid.

2, long2ip - Convert the number format into an IPV4 string Internet protocol

string long2ip ( string $proper_address )

Parameters: proper_address The correct address of the long integer express.

Return value: Returns the Internet address as a string.

3. How to use

$ip = '10.1.1.1';
$ip_long = ip2long($ip);
echo $ip_long.PHP_EOL; // 167837953
echo long2ip($ip_long); // 10.1.1.1

4. Reasons for negative numbers and how to deal with them

When the IP address is relatively large, Negative numbers will appear in ip2long:

$ip = '192.168.101.100';
$ip_long = ip2long($ip);
echo $ip_long.PHP_EOL; // -1062705820
echo long2ip($ip_long); // 192.168.101.100

Reason explanation:

IPv4 uses unsigned 32-bit addresses, so there are at most 2 to the 32nd power minus 1 (4294967295) addresses. . Write decimal numbers separated by 4 decimal points.

Remember as A.B.C.D, for example: 192.168.100.100.

Each decimal number in the IPv4 address is an unsigned byte, ranging from 0 to 255. Converting the IPv4 address to an unsigned number actually means placing each decimal number in the corresponding 8 bits, forming a 4-byte unsigned integer. 192.168.100.100, 192,168 in the high 8 digits and 100,100 in the low 8 digits.

Solution:

Use %u to format the output as an unsigned integer.

$ip = '192.168.101.100';
$ip_long = sprintf('%u',ip2long($ip));
echo $ip_long.PHP_EOL; // 3232261476 
echo long2ip($ip_long); // 192.168.101.100

Related tutorial recommendations: "PHP Tutorial"

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