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PHP extensions, php.ini and OPcache on Windows

Verified 1 min read

Load only the extensions an app needs, keep php.ini per PHP version, tune OPcache safely and verify the loaded configuration.

Tested onStandard / Datacenter · Build 26100.33650 · x64
E1
Build
26100.33650
Edition
Standard / Datacenter
Architecture
x64
Support
Documentation (E1)
Evidence
E1Official documentation
Verified
2026-10-29
Page type
Task

The short answer

Section titled “The short answer”

Three files matter:

  • php.ini — the loaded configuration;
  • ext\ — the extension DLLs;
  • php.ini’s extension_dir — where PHP looks for them.

Verify before debugging:

Terminal window
php --ini
php -m
php -i | Select-String "Loaded Configuration|extension_dir"

If Loaded Configuration File is not the file you edited, nothing else matters.

Extensions

Section titled “Extensions”
extension_dir="ext"
extension=curl
extension=mbstring
extension=openssl
extension=pdo_mysql
extension=mysqli

Enable only what the app uses. Each extension adds code and patch surface. On Windows the DLL name is usually php_<name>.dll; extension=curl resolves it under extension_dir.

If an extension fails to load, check:

  • the DLL exists in ext;
  • it matches the PHP version/TS-NTS/compiler;
  • its dependent DLLs are present;
  • the PHP error log says which one failed.

Per-version and per-site php.ini

Section titled “Per-version and per-site php.ini”

With multiple PHP versions, each directory has its own php.ini. Do not copy one ini across major versions and expect the extension ABI to match.

For a site-specific ini, set PHPRC in the FastCGI environment to that directory. Keep it explicit; otherwise PHP may load C:\Windows\php.ini or a previous version’s file.

OPcache

Section titled “OPcache”
opcache.enable=1
opcache.memory_consumption=128
opcache.max_accelerated_files=10000
opcache.validate_timestamps=1
opcache.revalidate_freq=2
  • validate_timestamps=1 is safe for development and small sites; PHP checks file mtimes.
  • validate_timestamps=0 is faster but requires a reload/restart after deploy; otherwise old code keeps running.
  • Do not enable experimental JIT “because faster” without testing the app and measuring.

Verify:

Terminal window
php -i | Select-String "opcache.enable|opcache.memory"

A phpinfo page shows the same, but remove it after testing.

Production baseline

Section titled “Production baseline”
expose_php=Off
display_errors=Off
log_errors=On
error_log="C:\PHP\logs\php-error.log"
date.timezone=UTC
memory_limit=256M
max_execution_time=60
upload_max_filesize=32M
post_max_size=32M

post_max_size must be >= upload_max_filesize, and IIS/Nginx limits must be >= both.

Verify

Section titled “Verify”
Terminal window
php --ini
php -m
php -r "echo ini_get('memory_limit'), PHP_EOL;"

Then call a page that uses the extension (PDO, curl, mbstring) instead of trusting php -m alone.

Lab boundary

Section titled “Lab boundary”

E1. PHP 8.4.27 FastCGI was verified on VM 361; extension/OPcache settings were not load-tested on Server 2025.

Sources