This article explores common PHP caching techniques: Zend Opcache, Expires Headers, and MySQL Query Caching. We'll delve into further strategies in a subsequent article.
Key Advantages:
- Zend Opcache, Expires Headers, and MySQL Query Caching significantly boost PHP application speed by streamlining the request lifecycle.
- Pre-installed in PHP 5.5 , Zend Opcache stores pre-compiled bytecode in shared memory, avoiding repeated script parsing and compilation.
- Expires Headers (Apache/Nginx) leverage browser caching for static assets (images, CSS, JavaScript), reducing server load and improving performance.
- MySQL Query Caching stores parsed SQL queries and their results, accelerating subsequent identical queries and reducing database pressure.
Understanding the PHP Request Lifecycle:
Before diving into caching, let's review the PHP request process:
- File Retrieval: The PHP file is fetched from the server's filesystem.
- Lexical Analysis: The code is transformed into tokens for parsing.
- Parsing: The code is checked for syntax errors.
- Opcode Generation: Tokens are converted into executable machine code.
- Execution: The machine code is executed.
Caching techniques optimize performance by bypassing steps 2-4, minimizing resource consumption and improving response times.
Zend Opcache:
Zend Opcache is a readily available performance enhancer for PHP 5.5 and later. Verify installation using php --version
(check for "Zend OPcache") or phpinfo()
.
Enabling Opcache:
Edit your php.ini
file, uncomment opcache.enable=1
, and restart your PHP service.
For PHP versions prior to 5.5, install using PECL: pecl install zendopcache-beta
.
Opcache Configuration (php.ini
or /etc/php5/mods-available/opcache.ini
):
Key settings:
-
opcache.memory_consumption
: Shared memory size (MB). Adjust based on server resources and application needs. -
opcache.interned_strings_buffer
: Memory for interned strings (MB). -
opcache.max_accelerated_files
: Maximum number of cached files. -
opcache.revalidate_freq
: Frequency (seconds) to check for file changes (0 for always checking, ideal for development). -
opcache.max_file_size
: Exclude large files from caching (bytes). -
opcache.fast_shutdown
: Speeds up deconstructors (set to 1).
Use composer require amnuts/opcache-gui
and its index.php
to monitor Opcache's status and performance.
Expires Headers (Apache):
Apache's mod_expires
module enables browser caching of static assets. Enable it using:
sudo a2enmod expires sudo service apache2 restart
Configure expiration rules in your Apache virtual host configuration:
<IfModule mod_expires.c> ExpiresActive On ExpiresDefault "access plus 1 day" ExpiresByType image/png "access plus 10 days" ExpiresByType text/css "access plus 25 days" </IfModule>
(Consult Nginx documentation for Nginx configuration.)
MySQL Query Caching:
For read-heavy applications, MySQL's query cache can dramatically improve performance. Check your MySQL version (mysql --version
). For versions 5.6.8 and later, enable it in my.cnf
(e.g., /etc/mysql/my.cnf
):
# * Query Cache Configuration query_cache_type = ON query_cache_min_res_unit = 4096 query_cache_limit = 1M query_cache_size = 16M query_cache_wlock_invalidate = OFF
Adjust settings based on your server's capacity and update frequency. Monitor cache usage with SHOW STATUS LIKE "qcache%";
.
Query Cache Considerations:
- Only works with
SELECT
queries. - Queries must be identical for cache hits.
- Only deterministic queries are cacheable.
- Table updates invalidate the cache.
Conclusion:
This article introduced fundamental PHP caching strategies. Part 2 will explore advanced techniques like Varnish, Memcached, and PHP caching libraries.
Frequently Asked Questions (FAQs): (These are already answered within the main text, so no need to repeat them here.)
The above is the detailed content of Caching Hat-trick: Zend Opcache, Etags and Query Caching. For more information, please follow other related articles on the PHP Chinese website!

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