Powered by
Known Issues

Known Issues

# Fibers

Calling PHP functions and language constructs that themselves call cgo in Fibers is known to cause crashes.

This issue is being worked on by the Go project.

In the meantime, one solution is not to use constructs (like echo) and functions (like header()) that delegate to Go from inside Fibers.

This code will likely crash because it uses echo in the Fiber:

$fiber = new Fiber(function() {
    echo 'In the Fiber'.PHP_EOL;
    echo 'Still inside'.PHP_EOL;

Instead, return the value from the Fiber and use it outside:

$fiber = new Fiber(function() {
    Fiber::suspend('In the Fiber'.PHP_EOL));
    Fiber::suspend('Still inside'.PHP_EOL));
echo $fiber->start();
echo $fiber->resume();

# Unsupported PHP Extensions

The following extensions are known not to be compatible with FrankenPHP:

imapNot thread-safejavanile/php-imap2, webklex/php-imap
newrelicNot thread-safe-

# Buggy PHP Extensions

The following extensions have known bugs and unexpected behaviors when used with FrankenPHP:

ext-opensslWhen using a static build of FrankenPHP (built with the musl libc), the OpenSSL extension may crash under heavy loads. A workaround is to use a dynamically linked build (like the one used in Docker images). This bug is being tracked by PHP.

# get_browser

The get_browser() function seems to perform badly after a while. A workaround is to cache (e.g. with APCu) the results per User Agent, as they are static.

# Standalone Binary and Alpine-based Docker Images

The standalone binary and Alpine-based docker images (dunglas/frankenphp:*-alpine) use musl libc instead of glibc and friends, to keep a smaller binary size. This may lead to some compatibility issues. In particular, the glob flag GLOB_BRACE is not available

# Using with Docker

By default, FrankenPHP generates a TLS certificate for localhost. It’s the easiest and recommended option for local development.

If you really want to use as a host instead, it’s possible to configure it to generate a certificate for it by setting the server name to

Unfortunately, this is not enough when using Docker because of its networking system. You will get a TLS error similar to curl: (35) LibreSSL/3.3.6: error:1404B438:SSL routines:ST_CONNECT:tlsv1 alert internal error.

If you’re using Linux, a solution is to use the host networking driver:

docker run \
    -e SERVER_NAME="" \
    -v $PWD:/app/public \
    --network host \

The host networking driver isn’t supported on Mac and Windows. On these platforms, you will have to guess the IP address of the container and include it in the server names.

Run the docker network inspect bridge and look at the Containers key to identify the last currently assigned IP address under the IPv4Address key, and increment it by one. If no container is running, the first assigned IP address is usually

Then, include this in the SERVER_NAME environment variable:

docker run \
    -e SERVER_NAME="," \
    -v $PWD:/app/public \
    -p 80:80 -p 443:443 -p 443:443/udp \


Be sure to replace with the IP that will be assigned to your container.

You should now be able to access from the host machine.

If that’s not the case, start FrankenPHP in debug mode to try to figure out the problem:

docker run \
    -e CADDY_GLOBAL_OPTIONS="debug" \
    -e SERVER_NAME="" \
    -v $PWD:/app/public \
    -p 80:80 -p 443:443 -p 443:443/udp \

# Composer Scripts Referencing @php

Composer scripts may want to execute a PHP binary for some tasks, e.g. in a Laravel project to run @php artisan package:discover --ansi. This currently fails for two reasons:

  • Composer does not know how to call the FrankenPHP binary;
  • Composer may add PHP settings using the -d flag in the command, which FrankenPHP does not yet support.

As a workaround, we can create a shell script in /usr/local/bin/php which strips the unsupported parameters and then calls FrankenPHP:

#!/usr/bin/env bash
for i in "$@"
    if [ "$i" == "-d" ]; then
        unset 'args[$index]'
        unset 'args[$index+1]'

/usr/local/bin/frankenphp php-cli ${args[@]}

Then set the environment variable PHP_BINARY to the path of our php script and composer should pass:

export PHP_BINARY=/usr/local/bin/php
composer install
Edit this page