How to verify if input is an IPv6 address using PHP regex

IPv6 refers to Internet Protocol Version 6, an IP address protocol used for Internet communication. An IPv6 address is a number composed of 128 bits, usually represented by eight hexadecimal number groups. In PHP, you can use regular expressions to verify whether the input is an IPv6 address. Here's how to use PHP regular expressions to verify IPv6 addresses.

Step one: Understand the format of the IPv6 address

The IPv6 address consists of 8 hexadecimal blocks, each block separated by a colon (:). Each hexadecimal block must be 4 hexadecimal digits. Here are some examples of IPv6 addresses:

2001:0db8:85a3:0000:0000:8a2e:0370:7334
fe80::1
::1

in IPv6 In the address, there are several special rules that need to be noted:

• You can use "::" to represent consecutive 0 blocks, but they can only appear once;
• If the IPv6 address contains If there are multiple "::", you need to fill in 0 before one of the "::";
• The IPv6 address cannot start with ":" or end with ":".

Step 2: Write PHP regular expression

In PHP, you can use the preg_match function to perform regular expression matching. Here is an example PHP regular expression to verify that the input is an IPv6 address:

function is_ipv6_address($address) {
return preg_match('/^(

  (([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4})| # 1: full IPv6 address
  (([0-9a-fA-F]{1,4}:){1,7}:)                  # 2: compressed IPv6 address with leading zeros
  (:([0-9a-fA-F]{1,4}:){1,6})                  # 3: compressed IPv6 address with intermediate zeros
  (([0-9a-fA-F]{1,4}:){1,5}:)                  # 4: compressed IPv6 address with leading and intermediate zeros
  ((:[0-9a-fA-F]{1,4}){1,5}:)                  # 5: compressed IPv6 address with trailing zeros
  ((:[0-9a-fA-F]{1,4}){1,4}:)                  # 6: compressed IPv6 address with leading, intermediate and trailing zeros
  ((:[0-9a-fA-F]{1,4}){1,3}:)                  # 7: compressed IPv6 address with leading, intermediate and trailing zeros
  ((:[0-9a-fA-F]{1,4}){1,2}:)                  # 8: compressed IPv6 address with leading, intermediate and trailing zeros
  ((:[0-9a-fA-F]{1,4}){1,1}:)                  # 9: compressed IPv6 address with leading, intermediate and trailing zeros
  )$/i', $address);

}

The main part of this regular expression is the regular expression used to match the various parts of the IPv6 address. It includes the following 9 regular expressions:

• The complete IPv6 address, For example, 2001:0db8:85a3:0000:0000:8a2e:0370:7334;
• An IPv6 address with consecutive 0s, such as fe80::1;
• A compressed IPv6 address with leading 0s, For example, 2001:db8:85a3::8a2e:370:7334;
• Compressed IPv6 address with middle 0 and leading 0, such as 2001:db8::8a2e:370:7334;
• Middle 0 and a compressed IPv6 address with trailing 0, such as 2001:db8:85a3::7334;
• A compressed IPv6 address with leading 0, middle 0, and trailing 0, such as ::1; , compressed IPv6 address with middle 0 and trailing 0, for example::;
• Compressed IPv6 address with leading 0, middle 0 and trailing 0, for example::db8:85a3:0:0:8a2e:370:7334 ;
• Compressed IPv6 address with leading 0, middle 0 and trailing 0, for example::db8:85a3:0:8a2e:370:7334.
• Step 3: Use PHP Code to verify IPv6 address

After writing the above regular expression, you can use the following PHP code to verify whether the input is an IPv6 address:

$address = "2001:0db8:85a3:0000: 0000:8a2e:0370:7334";

if (is_ipv6_address($address)) {

echo "The input is an IPv6 address";
} else {
echo "The input is not an IPv6 address";
}

In this code, an IPv6 address string $address is first defined, and the string is verified using the is_ipv6_address function. If the string is an IPv6 address, the output is "The input is IPv6 address", otherwise the output is "The input is not an IPv6 address".

Summary

In PHP, you can use regular expressions to verify whether the input is an IPv6 address. First understand the format of the IPv6 address, Then write an appropriate regular expression and use the preg_match function to match. After testing, the above regular expression can correctly verify the IPv6 address.

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