1、概述
字节码 缓存 不是 PHP 的新特性,有很多独立的扩展可以实现,比如APC、eAccelerator和Xache等,但是截至目前这些扩展都没有集成到PHP内核,从PHP 5.5.0开始,PHP内置了字节码缓存功能,名为Zend Opcache 。
开始之前,我们先来看看什么是字节码缓存,以及字节码缓存的作用是什么。
众所周知,PHP是解释型语言,构建在Zend 虚拟机之上,PHP解释器在执行PHP脚本时会解析PHP脚本代码,把PHP代码编译成一系列Zend操作码(opcode: http://php.net/manual/zh/internals2.opcodes.php ,由于每个操作码都是一个字节长,所以又叫字节码,字节码可以直接被Zend虚拟机执行),然后执行字节码。每次请求PHP文件都是这样,这会消耗很多资源,如果每次HTTP请求都必须不断解析、编译和执行PHP脚本,消耗的资源更多。如果PHP源码不变,相应的字节码也不会变化,显然没有必要每次都重新生成Opcode,结合在Web应用中无处不在的缓存机制,我们可以把首次生成的Opcode缓存起来,这样下次直接从缓存取,岂不是很快?下面是启用Opcode缓存之前和之后的流程图:
字节码缓存能存储预先编译好的PHP字节码,这样,下次请求PHP脚本时,PHP解释器不用每次读取、解析和编译PHP代码,直接从内存中读取预先编译好的字节码,然后立即执行,这样能省很多时间,极大提升应用的性能。
2、启用Zend Opcache
注:如果使用Windows开发环境,或者使用 brew 或 apt-get 等命令安装的PHP可以略过编译步骤。
默认情况下,Zend Opcache没有开启,需要我们在编译时使用 --enable-opcache 指定启用Zend Opcache。
编译好PHP后还需要在 php.ini 中指定Opcache扩展路径:
zend_extension=/path/to/opcache.so
一般而言PHP编译成功后会显示Zend Opcache扩展路径,但如果想不起来,可以使用如下命令找到PHP扩展所在目录:
php-config --extension-dir
注:如果你使用Xdebug,需要在 php.ini 中先加载Zend Opcache,再加载Xdebug。
更新 php.ini 后重启PHP进程并查看是否启用成功:
3、配置Zend Opcache
启用Zend Opcache后还需要在 php.ini 中配置Zend Opcache,下面是一份配置示例作为参考:
opcache.validate_timestamps=1 //生产环境中配置为0opcache.revalidate_freq=0 //检查脚本时间戳是否有更新时间opcache.memory_consumption=64 //Opcache的共享内存大小,以M为单位opcache.interned_strings_buffer=16 //用来存储临时字符串的内存大小,以M为单位opcache.max_accelerated_files=4000 //Opcache哈希表可以存储的脚本文件数量上限opcache.fast_shutdown=1 //使用快速停止续发事件
注:后续我们还会进一步介绍Zend Opcache的配置,PHP官网中列出了Zend Opcache的全部设置: http://ua2.php.net/manual/zh/opcache.configuration.php 。
4、使用Zend Opcache
Zend Opcache使用起来很简单,因为启用之后它会自动运行,Zend Opcache会自动在内存中缓存预先编译好的PHP字节码,如果缓存了某个文件的字节码,就执行对应的字节码。
如果 php.ini 中配置了 opcache.validate_timestamps 值为0,需要小心,因为Zend Opcache将不能觉察PHP脚本的变化,必须手动清空Zend OPcache缓存的字节码,才能让它发现PHP文件的变动。这个配置适合在生产环境中设置为0,但在开发环境会带来不便,我们可以在开发环境中这样配置启用自动验证缓存功能:
opcache.validate_timestamps=1opcache.revalidate_freq=0

What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python are both high-level programming languages that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.


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