OPcache is a built-in PHP extension that dramatically improves performance by storing precompiled script bytecode in shared memory. This eliminates the need for PHP to load and parse scripts on every request, reducing server load and speeding up website response times.

When a PHP script runs without OPcache, the server must:

• Read the script file from disk
• Parse and compile it into bytecode
• Execute the bytecode

This process repeats for every single request, consuming valuable CPU and memory resources.

With OPcache enabled:

• PHP scripts are compiled once and cached in memory
• Subsequent requests use the cached bytecode
• Script execution becomes significantly faster

The performance improvement can be substantial—often reducing server response times by 50% or more for PHP-heavy websites.

Most quality hosting providers enable OPcache by default on their servers. You can verify its status by creating a phpinfo() file or checking your hosting control panel. For optimal performance, ensure your applications are compatible and consider configuring OPcache settings like memory allocation and validation frequency.