PHP on Scalingo


Your application will be detected as a PHP application if:

  • There is a composer.lock file at the root of your project
  • index.php is present in the root directory (legacy app)


A stack based on Nginx and PHP-FPM will be installed.

Default Configuration

The default configuration for your application is defined in the buildpack’s php.ini and php-fpm.ini. You can see on these files the configuration for parameters such as upload_max_filesize and post_max_size.

PHP Versions


The following PHP versions are compatible with the platform:

  • 7.0 (up to 7.0.33, only for scalingo-18)
  • 7.1 (up to 7.1.33, only for scalingo-18)
  • 7.2 (up to 7.2.34, only for scalingo-18)
  • 7.3 (up to 7.3.33, only for scalingo-18)
  • 7.4 (up to 7.4.32, only for scalingo-18 and scalingo-20)
  • 8.0 (up to 8.0.28, only for scalingo-18 and scalingo-20)
  • 8.1 (up to 8.1.17)
  • 8.2 (up to 8.2.4)

Select a Version

By default, the latest 7.4 version of PHP will be installed, if you need to install a precise version it should be mentioned in your composer.json file.

Example to install the latest PHP version from the 8.0 branch:

  "require": {
    "php": "^8.0"

It installs the version 8.0.25 at the time of writing.


Composer is the official package manager for PHP. The official website is here. It aims at handling the dependency management of your application: installing dependencies and freezing their versions.

If composer is used in a project, the deployment system will detect it and use it to install the dependencies of the project.


This file defines the different dependencies used by your application. It is also used to configure custom deployment settings for the project (see below).


Once the third-party libraries have been defined, their versions need to be frozen in order to ensure a precise version of the application will always deploy a compatible set of Composer packages. These versions will be written in a compose.lock file. This file is required as it is read during the deployment on the platform.

To generate compose.lock you need to run:

$ composer install

When you need to upgrade a library, for instance slim:

$ composer update slim/slim

After each command, the composer.lock file will be updated automatically, do not forget to commit the modifications of the file.

Private Dependency

If you want to install a private dependency, you need to define the COMPOSER_AUTH environment variable on your application as specified in the Composer documentation. For instance, for a GitHub hosted private dependency, the COMPOSER_AUTH environment variable should contain:

  "github-oauth": {
    "": "MY-TOKEN"

MY-TOKEN must be replaced with a valid token of your GitHub account.

Composer During the Deployment

It is considered that when an application is deployed on Scalingo, it is run in “production” mode. As a result, composer install is run with the flag --no-dev.

If, in order to debug an application, development dependencies should be installed, please set the following environment variable:


Select a Composer Version

You can select the Composer version to install for your application deployment by specifying it in your composer.json:

  "extra": {
    "paas": {
      "engines": {
        "composer": "1.x"

Scalingo supports the following versions of Composer:

  • 2.2.18
  • 2.3.10
  • 2.4.4
  • 2.5.5

Native PHP Extensions

Applications might require native PHP extensions, these extensions are usually written in C and need to be compiled as shared libraries (.so files) and be used by PHP.

Some of them are bundled by default with the deployed version of PHP, the others are installed dynamically if specified in the project composer.json.

Native Extension Dependency

If an application requires a native PHP extension, it should be added in the require block of its composer.json:

  "require": {
    "ext-mongodb": "*",
    "ext-imagick": "*",

These dependency instructions are parsed by the deployment system which will install the require files.

List of Pre-Installed Extensions

These extensions are available by default with the installed version of PHP:

List of Available Extensions

These extensions will be installed dynamically if required in the composer.json file.

  • APC User Cache: apcu
  • MongoDB Driver: mongodb
  • MongoDB Legacy Driver: mongo, obsolete, only PHP 5.6
  • Redis Driver: redis
  • Image manipulation with ImageMagick: imagick
  • Memcached driver: memcached
  • Event : event
  • GMP Multiple Precisions math functions: gmp
  • FTP Client: ftp
  • IMAP: imap
  • Tidy: tidy
  • Calendar: calendar
  • Data Structures: ds, incompatible with PHP 8.0 and above
  • Lua: lua, incompatible with PHP 8.0 and above
  • Gettext: gettext
  • mcrypt: mcrypt, automatically installed with all apps with PHP 7.1 and before. External dependency starting with PHP 7.2.
  • Sodium sodium, incompatible with PHP 7.1 and below
  • Always Populate Form Data apfd
  • Extension’s missing: contact us, the support for it will be added quickly

Officially Supported Frameworks

Scalingo supports out-of-the-box many well-known frameworks. When using such frameworks, you have nothing special to configure in your composer.json, git push your code and everything will work!

List of the frameworks:

Configuration Tweaks

Setup Basic Authentication

You may want to hide your application behind an authentication gateway. You can configure HTTP basic auth for your application.

PHP-FPM Concurrency

The level of concurrency configured is defined automatically according to the size of the containers of your application. If you want to override this value, you can define the environment variable: WEB_CONCURRENCY. It directly modifies the pm.max_children parameter of PHP-FPM, defining the upper limit of how many workers handling incoming requests will be running. Each of these processes will be able to run 1 request at a time.

The default values for pm.max_children are based on the memory_limit parameter of the PHP configuration, the used formula is: floor(available_memory / php_memory_limit) + 2

Container Size Default Concurrency
S 3
M 3
L 7
XL 12
2XL 22
3XL 43

Concurrency Fine Tuning

Fine tuning the value of the WEB_CONCURRENCY environment variable is a bit tricky and must be handled with care. There is no magic formulae and one must load test his application to find the best value matching his use case. If the application is swapping, you might need to lower the value of WEB_CONCURRENCY and increase the amount of containers. On the contrary, if your application does not use all his memory, one can try to slightly increase the WEB_CONCURRENCY value and make sure the application does not start swapping.

Note that if the WEB_CONCURRENCY value is too high your application will not be 100% available. You will see at some point the following error message in your application logs, multiple times:

connect() to unix:/tmp/php-fpm.sock failed (11: Resource temporarily
unavailable) while connecting to upstream, client: XXX.XXX.XXX.XXX, server:
localhost, request: "GET / HTTP/1.1", upstream:
"fastcgi://unix:/tmp/php-fpm.sock:", host: ""

It happens when the PHP-FPM requests queue is full. Restarting your application empties this requests queue and makes your application back up. Then you should improve the value of the WEB_CONCURRENCY value.

Buildpack Custom Configuration

The buildpack allows you to configure precisely how your application is deployed. This configuration is done in your composer.json at the root of your project.

All these fields are optional, define them if you need to modify their default value.

   // Your content
  "extra": {
    // default values of PaaS specific instructions
    "paas": {
      "document-root": "",
      "index-document": "index.php",
      "engines": {
        "nginx": "default"
      "framework": "",
      "php-config": [],
      "php-includes": [],
      "php-fpm-config": [],
      "php-fpm-includes": [],
      "nginx-includes": [],
      "log-files": [],
      "compile": [],
      "new-relic": false,
      "access-log-format": ""


The directory where Nginx will define the root of your app.

This parameter can also be overridden with the DOCUMENT_ROOT environment variable.


Bypass framework detection by specifying the framework you want. It could also be useful if you need to specify your application does not use any framework. This is done by specifying default in the .extra.paas.framework configuration.


Name of the index document of each directory. When accessing a directory (, Nginx looks by default for an index.php file to execute, if your project is using another name, specify it here.


Define a specific version of Composer to use. By default your application uses the latest Composer version available. Most of the time, you don’t need to change this value.


Define a precise version of Nginx to use. By default your application is reachable through the last stable version of the server. Most of the time, you don’t need to change this value.

Scalingo supports the following versions of Nginx:

  • 1.14.2
  • 1.15.8
  • 1.16.1
  • 1.17.6
  • 1.18.0
  • 1.19.10
  • 1.20.1
  • 1.22.1


List of directives which will be added to your php.ini. The default values used for your application are in the buildpack’s php.ini.


  "php-config": [


List of directives which will be added to your php-fpm.ini.


  "php-fpm-config": [


Extra files which will be included in the php.ini.


Extra files which will be included in the php-fpm.ini.


Extra files which will be included in the Nginx configuration of your application. These files are injected at the http scope of the configuration file.


Extra files which will be included in the Nginx configuration of your application. These files are injected at the server scope of the configuration file.


Commands to run after the dependency installation.


  "compile": [
    "php app/console assetic:dump --env=prod --no-debug"


If your project is writing in custom log files, you can specify them here and they will be streamed to the logs of your application.

Your can read the logs on your dashboard or with the Scalingo CLI utility.

If true, enable New Relic instrumentation tools.

The environment variable named NEW_RELIC_LICENSE_KEY is required.

It is also highly recommended to include the NEW_RELIC_APP_NAME environment variable to specify the name of the application as displayed in the New Relic UI.


The format of the logs produced by the proxy Nginx for each request to your application.

It is empty by default, it means that Nginx will use the following format:

'$http_x_forwarded_for - "$request" $status $body_bytes_sent "$http_referer" "$http_user_agent"'

e.g. - "GET / HTTP/1.1" 200 1761 "" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:51.0) Gecko/20100101 Firefox/51.0"

When defining a custom value for the log format, please refer to the Nginx documentation page..

This parameter can also be overridden with the ACCESS_LOG_FORMAT environment variable.

Warning: .htaccess Files

Legacy projects often use .htaccess file in their project to modify the configuration of the Apache server. As the buildpack is based on Nginx and PHP-FPM, these files are ineffective.

Instead of using these files, you have to write directives for Nginx and configure the nginx-includes part of your composer.json. It can contains one or more configuration files:

  "extra": {
    "paas": {
      "nginx-includes": ["path/to/nginx_conf_file", ]

Example: Configuring Rate Limiting

In the following example we will set a rate limit of one request per second per IP.

Create a nginx-http.conf file at the root of your project:

limit_req_zone $binary_remote_addr zone=mylimit:10m rate=1r/s;

Then create a nginx-app.conf file at the root of your project:

location /login {
    limit_req zone=mylimit;
    try_files $uri $uri/ /index.php?$query_string;

Then modify your composer.json to add nginx-http-includes and nginx-includes config:

  "extra": {
    "paas": {
      "nginx-http-includes": ["nginx-http.conf"],
      "nginx-includes": ["nginx-app.conf"]

Example: URL Rewriting (e.g. WordPress)

Here is an example of legacy .htaccess which won’t work on Scalingo. You need to replace it with the Nginx configuration following the example.

Legacy .htaccess example:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

Nginx configuration:

location / {
  try_files $uri $uri/ /index.php?$args;

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PHP on Scalingo

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