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.

ipv4_conversion.php

<?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.

ipv6_conversion.php

<?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.

error_handling.php

<?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.

database_storage.php

<?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.

network_conversion.php

<?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

PHP inet_ntop Documentation

This tutorial covered the PHP inet_ntop function with practical examples for IP address conversion between binary and string formats.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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