Using a Reverse Proxy with PHP

Reverse proxies terminate TLS or route requests to PHP services behind a trusted layer.

What It Does

Reverse proxies terminate TLS or route requests to PHP services behind a trusted layer. The following examples distinguish a normal use case, a boundary case and a practical application.

Requirements and Compatibility

PHP 8.x and a local test environment. Apply input validation, correct error handling and the requirements of any optional libraries.

The code focuses on the core concept. Production implementation may also need routes, validation, persistence, authorization or deployment tooling.

Example 1: Basic Behavior

Understand the primary operation and its inputs.

<?php
$trusted = ['10.0.0.10'];
$peer = '10.0.0.10';
$forwarded = '198.51.100.11';
$ip = in_array($peer, $trusted, true) ? $forwarded : $peer;
echo $ip;

Example 2: Another Case

Check failure behavior or a different execution path.

<?php
$peer = '203.0.113.7';
$header = '127.0.0.1';
$ip = $peer; // Ignore X-Forwarded-For from an untrusted peer
echo $ip;

Practical Example: Putting It to Use

Only trust forwarded scheme and host metadata from your configured reverse proxy.

<?php
$trustedProxy = '10.0.0.5'; $directPeer = '203.0.113.12';
$forwardedProto = 'https';
$scheme = $directPeer === $trustedProxy ? $forwardedProto : 'http';
echo $scheme;

Important Behavior and Edge Cases

Only honor forwarding headers from explicitly trusted proxy addresses.

Comparison with Related Functions or Approaches

Common Beginner Mistakes

Key Takeaways

• Reverse proxies terminate TLS or route requests to PHP services behind a trusted layer.
• Only honor forwarding headers from explicitly trusted proxy addresses.
• Set correct trusted hosts and proxy policies in web-server and application configuration.

Before adapting these examples, verify the return values, test the failure paths and confirm that your application meets its security and environment requirements.