Analysis of the underlying development principles of PHP7: In-depth understanding of the working principle of OPcache

Analysis of the underlying development principles of PHP7: In-depth understanding of the working principle of OPcache

In recent years, with the development of the Internet, the number of web page visits has continued to increase, and the performance requirements for the website have It is also getting better and better. As a commonly used server-side programming language, PHP has attracted much attention in dealing with performance issues under high load conditions. The release of the PHP7 version has improved performance to a new level, mainly due to one of the new features: OPcache.

OPcache is an intermediate cache introduced in PHP7 to speed up the execution of PHP scripts. Its core principle is to cache PHP compiled bytecode into memory to avoid the need to re-parse and compile PHP scripts for each request, thus greatly improving PHP execution efficiency.

1. Installation and configuration of OPcache
First, we need to install the OPcache extension in PHP7. Normally, OPcache will be installed with PHP7 and only needs to be enabled in php.ini. Find the following configuration item in php.ini, uncomment it and set it to "On":

[opcache]
zend_extension=opcache.so
opcache.enable=1

Through the above configuration, we have successfully enabled the OPcache extension. But in a formal environment, we usually need to adjust the OPcache configuration according to the actual situation to achieve the best performance.

2. How OPcache works
When a PHP script is requested for the first time, the PHP parser will parse it into bytecode and store the bytecode in the cache of OPcache. If there is the same request next time, the PHP parser does not need to parse and compile the script again, and directly uses the bytecode in the cache for execution, which improves efficiency.

OPcache's cache is saved in file units, and each file has a unique cache ID in the cache. When a script is modified, its cache ID will change, and OPcache will automatically mark it as "invalid", indicating that it needs to be recompiled. In this way, when the next request comes, it will first be judged whether the cache ID is valid, and if it is invalid, it will be recompiled.

3. OPcache code example
Below we use a simple PHP code to demonstrate the working principle of OPcache. First, create a new file named "opcache_example.php" with the following content:

<?php
echo "Hello, OPcache!";
?>

Next, we write a simple PHP script to see the effect of OPcache:

<?php
$count = 10000;

$start_time = microtime(true);
for ($i = 0; $i < $count; $i++) {
    include 'opcache_example.php';
}
$end_time = microtime(true);

$total_time = $end_time - $start_time;
echo "Total time: " . $total_time . "s";
?>

In the above code, we use a simple for loop to include the "opcache_example.php" file multiple times. We can judge the effect of OPcache by counting the execution time of the loop.

Execute the script in the command line, you can see the following output:

Total time: 0.0023858547210693s

Next, we modify the "opcache_example.php" file and change the content to:

<?php
echo "Hello, OPcache! This is a modified version.";
?>

Execute the above script again and you can see the following output:

Total time: 0.75803589820862s

By comparing the execution time, we can clearly see the advantages of OPcache. The first time the script is executed, the PHP parser stores the bytecode of the "opcache_example.php" file into the OPcache cache. In subsequent loops, the bytecode in the cache is directly used for execution, so the execution time is very short. When the script is modified, the cache ID becomes invalid and the PHP parser needs to recompile the script, so the execution time increases significantly.

Through the above examples, we can have a deeper understanding of the working principle of OPcache and its important role in improving PHP performance.

4. Summary
This article explores in depth how the OPcache extension in PHP7 works and how to install and configure OPcache. Through a simple code example, it is explained how OPcache caches the bytecode of a PHP script into memory and directly uses the cache for execution in subsequent requests. Through reasonable configuration and use of OPcache, the execution efficiency of PHP scripts can be greatly improved and provide better performance for high-load websites.

However, as developers, we also need to pay attention to some potential problems. For example, frequent modifications to scripts during the development process will cause cache invalidation, thus affecting performance. Therefore, OPcache needs to be properly configured and managed in development and production environments to obtain optimal performance.

To sum up, an in-depth understanding of the working principle of OPcache can help developers better use OPcache to improve the performance of PHP code and provide users with a better experience.

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