PHP inet_ntop Function
last modified April 4, 2025
The PHP inet_ntop function converts a packed binary IP address
to a human-readable string format. It works with both IPv4 and IPv6.
Basic Definition
inet_ntop translates a binary IP address to standard notation.
It's the reverse of inet_pton which converts strings to binary.
Syntax: inet_ntop(string $ip): string|false. Returns the address
as a string or false on failure. Requires PHP 5.1.0 or later.
Convert IPv4 Address
This example demonstrates converting a packed IPv4 address to dotted notation.
<?php
declare(strict_types=1);
$packed = inet_pton("192.168.1.1");
$result = inet_ntop($packed);
echo "Packed: " . bin2hex($packed) . "\n";
echo "Unpacked: $result\n";
First we pack the IP string to binary with inet_pton, then
convert it back. The bin2hex shows the binary representation.
Convert IPv6 Address
This example shows converting a packed IPv6 address to its string format.
<?php
declare(strict_types=1);
$packed = inet_pton("2001:0db8:85a3:0000:0000:8a2e:0370:7334");
$result = inet_ntop($packed);
echo "Packed: " . bin2hex($packed) . "\n";
echo "Unpacked: $result\n";
IPv6 addresses are 128-bit compared to IPv4's 32-bit. The function handles both formats automatically based on input length.
Error Handling
This example demonstrates proper error handling when using inet_ntop.
<?php
declare(strict_types=1);
$invalid = "\x7f\x00\x00\x01\x00"; // Invalid length
$result = inet_ntop($invalid);
if ($result === false) {
echo "Invalid packed IP address\n";
} else {
echo "Converted: $result\n";
}
The function returns false for invalid input. Always check the return value to handle potential conversion failures gracefully.
Working with Database Storage
This example shows how to work with IP addresses stored in binary format.
<?php
declare(strict_types=1);
// Simulate IP from database (BINARY/VARBINARY column)
$db_ip = hex2bin("c0a80101"); // 192.168.1.1
$human_ip = inet_ntop($db_ip);
echo "Database IP: " . bin2hex($db_ip) . "\n";
echo "Human-readable: $human_ip\n";
Databases often store IPs in binary for efficiency. inet_ntop
converts them back to readable format when retrieved.
Network Address Conversion
This example demonstrates converting network addresses between formats.
<?php
declare(strict_types=1);
$network = hex2bin("ac100000"); // 172.16.0.0/12
$mask = hex2bin("fff00000"); // 255.240.0.0
$network_str = inet_ntop($network);
$mask_str = inet_ntop($mask);
echo "Network: $network_str\n";
echo "Mask: $mask_str\n";
Network addresses are often manipulated in binary form. This shows how to convert them to readable format for display or logging purposes.
Best Practices
- Validation: Always validate input before conversion
- Error Handling: Check for false return values
- Storage: Use binary format for database storage
- IPv6: Test with both IPv4 and IPv6 addresses
Source
This tutorial covered the PHP inet_ntop function with practical
examples for IP address conversion between binary and string formats.