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Install Howdah

Choose your system and get the exact commands to install, verify and roll back — one build per PHP minor version. Start in detect mode; the critical limits still block.

1. Operating system Debian / Ubuntu Ubuntu 16.04–24.04, Debian 11–12 — installs with apt RHEL / CentOS / Alma / Rocky CentOS 7, Alma/Rocky 8–9 (Remi layout) — installs with yum/dnf Other / panel / stock PHP Amazon Linux, cPanel, Plesk, CloudLinux, older distros — install from the signed tarball

2. Where your PHP comes from Surý PPA / deb.sury.org The usual source for modern PHP on Debian/Ubuntu The distribution's own PHP Same package format; use the tarball if your API number has no matching build

3. PHP version PHP minor version (from php -v)

4. Server type (SAPI) PHP-FPM The common setup behind Nginx or Apache Apache mod_php prefork mpm php-cgi / FastCGI See the note about CVE-2012-1823 below

Your commands

Showing the default: Debian/Ubuntu + Surý + PHP 8.1 + PHP-FPM. With JavaScript, the commands below update as you change the choices above. Without it, follow the full per-platform guide in the docs.

The package ships with howdah.mode = detect. When you want to change limits or turn a layer on, the config editor builds a validated howdah.toml and the matching ini lines, with a curl command to fetch it.

Add the signed apt repository

The key is pinned to this repository only.

sudo install -d -m 0755 /etc/apt/keyrings
curl -fsSL https://howdah.org/key.asc | sudo tee /etc/apt/keyrings/howdah.asc >/dev/null
echo "deb [signed-by=/etc/apt/keyrings/howdah.asc] https://pkg.howdah.org/apt stable main" \
  | sudo tee /etc/apt/sources.list.d/howdah.list

Install the package for your PHP
```
sudo apt-get update
sudo apt-get install php8.1-howdah
```
The package installs only against a PHP with the matching ABI, and enables the module for PHP 8.1.

Verify it is loaded, then reload your server

php -m | grep -i howdah
php --ri howdah          # Howdah => enabled, Mode => detect
sudo systemctl reload php8.1-fpm

Roll back at any time

sudo phpdismod -v 8.1 howdah        # stop loading, keep the package
sudo apt-get purge php8.1-howdah    # or remove everything
sudo systemctl reload php8.1-fpm

Your PHP comes from the distribution, not Surý. The package targets the Surý/Debian module layout and the matching ABI (phpapi-N). If apt reports no installation candidate for your version, your distribution's PHP has no matching build — switch to Other / stock PHP above and use the signed tarball.

The signing key is at https://howdah.org/key.asc — the same key that signs the release SHA256SUMS. Check its primary fingerprint, 1152 1035 C600 F638 31F8 2551 2087 B872 0997 807B, before trusting it. Package and metadata signatures are both enforced.

Install Howdah

Your commands

Add the signed apt repository

Install the package for your PHP

Verify it is loaded, then reload your server

Roll back at any time

A note for php-cgi / FastCGI