OpCache significantly improves execution efficiency by cached compiled PHP scripts, and its core is to avoid duplicate parsing and compilation. 1. After OpCache is enabled, the opcode is stored in shared memory, and subsequent requests can be executed directly; 2. Reduce CPU usage and disk I/O; 3. Key configurations include the on state, memory size, maximum cached files and verification frequency; 4. It is suitable for scenarios where code changes are small and access is large, but the effect is limited when dynamically generating code; 5. The status can be checked through phpinfo and enabled manually. Rationally configuring OpCache is an important means to optimize PHP performance.

OpCache plays a big role in speeding up PHP execution by reducing the overhead of recompiling PHP scripts every time they're requested. Without OpCache, PHP has to parse and compile your code into opcode (a low-level set of instructions) on every request — which takes time and resources. With OpCache enabled, that compiled code is stored in shared memory, so subsequent requests can skip the parsing and compiling steps entirely.

How OpCache works behind the scenes

When a PHP script runs for the first time, PHP parses the file, compiles it into opcode, and then executes it. If OpCache is enabled, that generated opcode gets stored in memory after the first run. On future requests, instead of parsing and compiling again, PHP checks if the cached version exists and is still valid. If yes, it skips straight to execution using the cached opcode.

• This cuts down CPU usage
• Reduces disk I/O since the script doesn't need to be read and processed every time
• Makes each request faster because fewer steps are involved

It's especially useful on busy sites where the same scripts are accessed frequently.

Key OpCache settings that affect performance

There are several configuration options you can tweak depending on your site's needs:

• opcache.enable – Turns OpCache on or off. Make sure this is enabled in production.
• opcache.memory_consumption – Controls how much memory is allocated for storing compiled scripts. Larger sites may need more than the default 64MB.
• opcache.max_accelerated_files – Sets the maximum number of files OpCache can handle. If you have a lot of PHP files, you might need to increase this.
• opcache.revalidate_freq – Determines how often (in seconds) OpCache checks if a script has changed. Setting this to 0 makes it check on every request, which is good for development but slows things down. In production, setting it higher improves performance.

These settings are usually adjusted in the php.ini file or through an .ini drop-in if you're on a managed server setup.

When OpCache helps the most (and when it doesn't)

OpCache shines brightest in environments where:

• Scripts don't change often (like production servers)
• There's a high volume of repeated requests
• You're running large apps with many PHP files

On the flip side, in local development settings where files change frequently, OpCache can actually get in the way unless configured properly. That's why developers sometimes disable it or set opcache.revalidate_freq=0 during active development.

Also, if your application uses dynamic code generation — like eval() or include files based on runtime logic — OpCache won't help those parts as much, because it can't cache dynamically generated code effectively.

Enabling and checking OpCache status

Most modern PHP installations come with OpCache bundled, but it might not always be enabled by default. To check if it's active:

• Create a phpinfo.php file with <?php phpinfo(); ?>
• Load it in your browser and look for the "OPCache" section

If you don't see it, you'll need to enable it manually. The process varies slightly depending on your OS and PHP setup, but generally involves editing your php.ini and adding or uncommenting:

 zend_extension=opcache.so
opcache.enable=1

Once enabled, restart your web server (Apache or Nginx) for the changes to take effect.

Basically that's it. Enabling and properly configuring OpCache is one of the easiest and most effective ways to improve PHP performance, especially in production environments.

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