Multi-PHP Version Management: Run PHP 5.6 to 8.5 Side by Side
Panelica lets you run five PHP versions simultaneously — each with independent extensions, configuration, and per-user PHP-FPM pools. Different sites can use different PHP versions on the same server with complete isolation.
In This Article
1. Five PHP Versions, One Server
Panelica ships with PHP 8.1, 8.2, 8.3, 8.4, and 8.5 — all compiled from source and installed under /opt/panelica/services/php/. Each version has its own binary, configuration directory, extensions, and PHP-FPM socket. They run completely independently.
Coverage extends across modern and legacy PHP. PHP 8.1 through 8.5 ship as native PHP-FPM binaries, while PHP 5.6, 7.0, 7.1, 7.2, 7.3, and 7.4 run inside transparent Docker-isolated runtimes. The same per-domain dropdown selects either tier; existing Panelica installations gain legacy coverage without CloudLinux or RPM dependencies.
Switching a domain's PHP version is a one-click operation in the panel. Behind the scenes, Panelica updates the Nginx upstream to point to the correct PHP-FPM socket and reloads the configuration. Zero downtime.
2. Per-User PHP-FPM Pool Isolation
This is where Panelica fundamentally differs from cPanel and Plesk. Instead of running all sites through a shared PHP-FPM master process, Panelica creates a separate PHP-FPM pool for each user, for each PHP version.
Process Isolation
Each pool runs as the site owner's Linux user — not www-data, not nobody. A PHP vulnerability in one site cannot access another user's files because the process literally runs as a different Unix user.
Resource Limits
Independent pm.max_children, pm.start_servers, and pm.min/max_spare_servers per pool. One runaway WordPress plugin can't consume all PHP workers on the server.
Security Sandbox
open_basedir restricts PHP file access to the user's home directory and /tmp. Combined with disable_functions for dangerous system calls. Each pool is a security sandbox.
Independent Restart
Restart PHP-FPM for a single user without affecting anyone else on the server. Debugging a PHP issue? Restart that one pool. Everyone else keeps running.
panelica-php-fpm-{version}-user@{username}.service — each pool is a systemd instantiated service, managed independently, with its own PID file and socket.
The pool configuration is generated at /opt/panelica/etc/php-fpm-users/{user}/{version}/pool.d/pool.conf and includes security hardening: open_basedir, disable_functions, upload_tmp_dir restrictions, and file permission enforcement.
3. Extension Management
Panelica manages 50+ PHP extensions per version through a GUI toggle interface. Extensions are managed via conf.d/ directory symlinks — enabling an extension creates a symlink, disabling removes it. PHP-FPM reloads automatically.
Core Extensions
json, spl, ctype, date, filter, hash, pcre, reflection, standard — always available, compiled into PHP.
Web & Database
curl, gd, imagick, openssl, zip, xml, mysqli, pdo_mysql, pdo_pgsql, sqlite3 — toggle on/off per version.
Caching & Performance
OPcache, APCu, Redis, Memcached — essential for WordPress and Laravel performance. Enable with one click.
PECL Extensions
Install PECL extensions asynchronously — the panel compiles them in the background and notifies you when ready. No SSH, no pecl install commands.
4. php.ini Configuration Per Domain
Global php.ini settings apply server-wide, but Panelica also supports per-domain overrides for critical settings:
| Setting | Global Default | Per-Domain Override |
|---|---|---|
| memory_limit | 256M | Up to plan limit |
| max_execution_time | 300s | Up to plan limit |
| upload_max_filesize | 128M | Per-domain configurable |
| post_max_size | 128M | Per-domain configurable |
| max_input_vars | 3000 | Per-domain configurable |
| max_file_uploads | 50 | Per-domain configurable |
Per-domain limits are stored in a domain_php_limits table with a unique constraint on (domain_id, php_version) — each domain can have different settings for each PHP version it uses.
Settings are validated with php -l syntax checking before applying, and PHP-FPM reloads only after validation passes. No more broken sites from a typo in php.ini.
5. Bulk Version Change
Upgrading PHP across multiple sites? Panelica's bulk version change endpoint lets you switch all sites (or a filtered subset) to a new PHP version in a single API call. The operation returns a detailed report showing which domains succeeded, which failed, and why.
POST /api/v1/php/bulk-change-version with {"source_version": "8.2", "target_version": "8.4"} — migrates all PHP 8.2 sites to 8.4. Response includes per-domain status with old/new versions.
6. System PHP & CLI
Panelica uses wrapper scripts (not symlinks) for system PHP commands at /usr/local/bin/. This is a deliberate architectural choice:
/etc/php/X.Y/cli/conf.d/ directory — which contains references to system extensions that aren't installed in Panelica's isolated PHP. This causes "Unable to load dynamic library" errors. Wrapper scripts set PHP_INI_SCAN_DIR to Panelica's conf.d directory, ensuring PHP loads the correct extensions.
Version-specific CLI commands (php81, php82, php83, php84, php85) let you run PHP scripts with any installed version directly from the command line.
Composer is also managed as a wrapper script using Panelica's own composer.phar binary — not Ubuntu's outdated packaged version (2.2.x) which throws deprecation notices with PHP 8.4+.
7. PHP Statistics Dashboard
The PHP management page shows real-time statistics: total installed versions, active PHP-FPM services, domains per version, most-used version, and default system version. Per-version detail pages show the list of domains using that version with their individual resource configurations.
8. cPanel vs Plesk vs Panelica PHP Comparison
| Feature | cPanel (MultiPHP) | Plesk | Panelica |
|---|---|---|---|
| PHP versions available | 5.6–8.3 (EA4) | 7.1–8.3 | 5.6 -> 8.5 (native + Docker shim, no CloudLinux required) |
| PHP-FPM isolation | Shared pool per version | Shared pool | Per-user per-version pool |
| Process runs as | nobody/www-data | www-data | Site owner's Linux user |
| open_basedir per user | Global setting | Per-domain | Per-pool enforced |
| Extension management | EasyApache GUI | GUI (limited) | GUI + async PECL install |
| Per-domain php.ini | .htaccess only | Limited | Full per-domain overrides |
| Bulk version change | No | No | Yes — API + GUI |
| Independent pool restart | No — restarts all | No | Yes — per user, per version |
| Version statistics | No | Basic | Full dashboard with per-version domain list |
| Cgroups v2 integration | No | No | Yes — PHP-FPM inside user cgroup slice |
9. Security Considerations
Panelica's PHP isolation goes beyond just open_basedir:
- Cgroups v2 integration: PHP-FPM pools run inside the user's cgroup slice — CPU, memory, and I/O limits are enforced at the kernel level, not just PHP's internal limits.
- disable_functions: Dangerous functions like
exec,system,passthru,shell_exec,proc_openare disabled per pool. Individual domains can have customized function blacklists. - Unix socket permissions: Each PHP-FPM socket is owned by
www-datawith mode0660— only Nginx and the socket owner can connect. No cross-user socket access. - Systemd hardening: PHP-FPM services use
Type=simplewith proper PID file management. No root escalation paths.
Run Multiple PHP Versions with Real Isolation
Per-user pools. Per-domain configs. Cgroups v2 enforcement. No shared-nothing compromises.
Start freePanelica — Where PHP isolation means actual Linux process isolation, not just an open_basedir directive.
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