Use get_client_version and filter_var() to determine IP legality

In PHP development, it is often necessary to verify whether the IP address provided by the user is legal. In many scenarios, especially when handling client connections or API requests, IP verification is a crucial feature. This article will explain how to use the get_client_version() function and PHP's built-in filter_var() function to determine whether the IP address is legal.

1. Obtain the client IP address

First, we need to get the IP address of the client. Typically, the client IP can be obtained by REMOTE_ADDR in the $_SERVER hyperglobal array, but in some cases, such as the use of a proxy server or load balancer, REMOTE_ADDR may return the proxy server's IP address instead of the client's real IP address. To ensure that the client's real IP address can be obtained correctly, we can use the following code:

 function get_client_ip() {
    if (!empty($_SERVER['HTTP_CLIENT_IP'])) {
        return $_SERVER['HTTP_CLIENT_IP'];
    } elseif (!empty($_SERVER['HTTP_X_FORWARDED_FOR'])) {
        return $_SERVER['HTTP_X_FORWARDED_FOR'];
    } else {
        return $_SERVER['REMOTE_ADDR'];
    }
}

The get_client_ip() function will prioritize the HTTP header fields HTTP_CLIENT_IP and HTTP_X_FORWARDED_FOR , which are often used to identify the client's real IP address. If these two fields have no values, REMOTE_ADDR is returned, that is, the default client IP.

2. Use filter_var() to verify the IP address

Next, we use PHP's filter_var() function to verify whether the IP address we obtained is legal. filter_var() is a very powerful function that allows you to check values ​​based on the type of verification passed in. For verification of IP addresses, we can use the FILTER_VALIDATE_IP option.

 $ip = get_client_ip();  // Get the clientIPaddress
if (filter_var($ip, FILTER_VALIDATE_IP)) {
    echo "IPaddress合法：$ip";
} else {
    echo "IPaddress不合法：$ip";
}

In this example, filter_var() will check whether the incoming $ip is a valid IP address. Return true if the IP address is legal, otherwise return false .

Supports IPv4 and IPv6

FILTER_VALIDATE_IP will verify IPv4 and IPv6 addresses. If you only need to verify IPv4 or IPv6 addresses, you can limit the type by specifying the flag:

 // verifyIPv4address
if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
    echo "IPv4address合法：$ip";
} else {
    echo "IPv4address不合法：$ip";
}

// verifyIPv6address
if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) {
    echo "IPv6address合法：$ip";
} else {
    echo "IPv6address不合法：$ip";
}

By using the FILTER_FLAG_IPV4 or FILTER_FLAG_IPV6 flags, we can only verify addresses of IPv4 or IPv6 types, respectively.

3. Comprehensive example: determine whether the IP address is legal and handle different situations

Finally, we can combine the get_client_ip() function and filter_var() function to write a complete example to determine whether the client IP address is legal and to handle it accordingly.

 // Get the clientIPaddress
$ip = get_client_ip();

// verifyIPaddress是否合法
if (filter_var($ip, FILTER_VALIDATE_IP)) {
    echo "IPaddress合法：$ip";
} elseif (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
    echo "IPv4address合法：$ip";
} elseif (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV6)) {
    echo "IPv6address合法：$ip";
} else {
    echo "IPaddress不合法：$ip";
}

In this example, we first try to verify the normal IP address, if it is not a normal IP, and then check whether it is a legitimate IPv4 or IPv6 address. If none of them meet the criteria, the output is "IP address is illegal".

Hopefully this article can help you understand how to use get_client_version() and filter_var() to verify whether the IP address is legal. If you have more questions about PHP development, feel free to ask questions!