This article was first published on GitBook.cn and can be published on third-party platforms due to the one-year exclusivity period. Due to the rush of time, coupled with the limited level of the author, there are shortcomings, and I hope that the majority of readers will bear with and guide.

Linguistic features

PHP is indeed a distinctive language (second only to Python)

Object-oriented

Since PHP5, PHP has a complete object model, including classes, abstract classes, interfaces, inheritance, constructors, reflections, cloning, and exceptions, among others. Here are the new features in PHP 5.3-PHP 7.2 regarding object orientation:

Namespace (PHP5.3, better organization classes)
Traits (PHP5.4, solves the problem of multiple inheritance scenarios)
Anonymous Class (PHP7.0)
Importing a Set of Classes (PHP7.0)
Visibility of Class Constants (PHP7.1)
Multi-Exception Capture Handling (PHP7.1)
Allows overriding abstract methods (PHP7.2)

Function Expressions

UNLIKE JAVA, PHP TREATS FUNCTIONS AS "FIRST-CLASS CITIZENS", AND IF YOU PREFER FUNCTIONAL PROGRAMMING, PHP WON'T DISAPPOINT YOU. Here are the new features in PHP 5.3-PHP 7.2 regarding functions:

Closures (PHP5.3)
闭包支持$this(PHP5.4)
Closure::call() (PHP7.0)

Asynchronous programming

As we all know, PHP is a single-threaded synchronous language. Prior to PHP 5.5, the only way to improve performance was to write code in a multi-process or multi-threading (pthreads) way. However, with the official introduction of PHP 5.5 Generator, asynchronous is possible. Here are the new features in PHP5.3-PHP7.2 for asynchronous programming:

Generator(PHP5.5)

Metaprogramming

PHP enables metaprogramming in a variety of ways through reflection APIs and magic methods. For example, it is possible to emulate the missing object-oriented feature of PHP - overloading - by magic methods. Here are the new features in PHP5.3-PHP7.2 regarding the magic method:

__callStatic (PHP5.3)
__invoke() (PHP5.3)

PHP Standard Library

The PHP standard library provides built-in data structures, iterators, interfaces, exceptions, functions, and file handling.

data structure

SplDoublyLinkedList 双链表
SplStack 栈
SplQueue 队列
SplHeap 堆
SplMaxHeap 最大堆
SplMinHeap minimum heap
SplPriorityQueue 优先队列
SplFixedArray 固定数组
SplObjectStorage object container

Iterators

AppendIterator 附加迭代器
ArrayIterator 数组迭代器
CachingIterator 缓存迭代器
CallbackFilterIterator — 回调过滤迭代器
DirectoryIterator — 目录迭代器
EmptyIterator — 空迭代器
FilesystemIterator — 文件系统迭代器
FilterIterator — 过滤迭代器
GlobIterator — Glob迭代器
InfiniteIterator — 无限迭代器
IteratorIterator — 迭代器迭代器
LimitIterator — 1,000,000,000
MultipleIterator — 多重迭代器
NoRewindIterator — 无倒回迭代器
ParentIterator — why not?
RecursiveArrayIterator — 𑀥
RecursiveCachingIterator — 递归缓存迭代器
RecursiveCallbackFilterIterator — 递归回调过滤迭代器
RecursiveDirectoryIterator — 递归目录迭代器
RecursiveFilterIterator — 递归过滤迭代器
RecursiveIterator — 𐕈ᬹᬹᬍᬹ
RecursiveRegexIterator — ʹ
RecursiveTreeIterator —the 𑁁 𑀢ᬶᨤ
RegexIterator — 正则迭代器

interface

Countable —可计算接口
OuterIterator —外部迭代器接口
RecursiveIterator(s)
SeekableIterator —可查找迭代器接口

abnormal

BadFunctionCallException —错误函数调用异常
BadMethodCallException —错误方法调用异常
DomainException —作用域异常
InvalidArgumentException —非法参数异常
LengthException —长度异常
LogicException —逻辑异常
OutOfBoundsException —违背安全原则异常
OutOfRangeException —越界索引异常
OverflowException —上溢异常
RangeException —范围异常
RuntimeException —运行时异常
UnderflowException —下溢异常
UnexpectedValueException —意外数值异常

function

class_implements — Returns all interfaces implemented by the specified class.
class_parents —Returns the parent class of the specified class
class_uses —Returns traits used by the specified class
iterator_apply —A user-defined function is called for each element in the iterator
iterator_count —Counts the number of elements in the iterator
iterator_to_array —Copies elements from the iterator to an array
spl_autoload_call — An attempt was made to call all registered __autoload() functions to mount the request class
spl_autoload_extensions — Registers and returns the default file extension used by spl_autoload function
spl_autoload_functions —Returns all registered __autoload() functions.
spl_autoload_register — Registers a given function as an implementation of __autoload
spl_autoload_unregister — Unregister the registered __autoload() function
spl_autoload — The default implementation of the __autoload() function
spl_classes - Returns all available SPL classes
spl_object_hash —返回指定对象的hash id

Document processing

SplFileInfo — The SplFileInfo class provides a high-level object-oriented interface to the information of a single file.
SplFileObject — SplFileObject provides an object-oriented interface for files.
SplTempFileObject — SplFileObject provides an object-oriented interface for temporary files.

Various classes and interfaces

ArrayObject — The ArrayObject class allows objects to be used as arrays
SplAbserver —The SplAbserver interface is used with the SplSubject to implement the observer design pattern.
SplSubject —SplSubject接口与SplObserver一起使用以实现观察者设计模式。

Why is the best language scolded?

MM: You can make everyone in this forum quarrel, and I'll go with you tonight. A software engineer: PHP is the best language! A certain forum is really fried, all kinds of quarrels...... A certain MM: I've served you, let's go, you can do whatever you want. A software engineer: Not today, I have to convince them that PHP must be the best language......

PHP is always the worst hacked in the chain of disdain for programming languages. But why do some people clamore PHP as the best language in the world, while others denounce PHP in all sorts of ways?

The learning threshold is low

By shielding more complex language features such as memory management, pointers, and C-like syntax, PHP beginners can quickly become familiar with the language. The nature of dynamic languages also makes type checking unperceptible to beginners. Coupled with an easy-to-build runtime environment, rich built-in APIs, and an active technical community, isn't this the "best language in the world" in the eyes of a beginner programmer?

Of course, this is also a fuse for being hacked, a programmer does not know pointers, asynchronous IO, threads, locks, enumerations, dictionaries, generics... Is this still a programmer?

Historical baggage

PHP is not like most well-known languages that were born in well-known organizations or companies. PHP originated in 1995, when the 17-year-old father of PHP (Rasmus Lerdorf) wrote a server script based on the Perl language to track and collect information about browsing his personal website. Since the main function of the first is to convert forms and collect information, this server-side script is named Personal Home Page Tools/Form Interperter, or PHP/FI for short. This is the original reason for the naming of PHP. Since PHP was originally intended to be just a tool, and Lerdorf was a very good programmer, language design was not his specialty, so PHP has a lot of historical baggage.

Confusing function naming, Linux C style coexists with camel naming
Misused string connectors (.)
Confused order of parameters
Lack of support for multithreading

Since PHP is consistently backwards compatible, PHP will still carry these burdens and strive forward.

The prejudice of the ignorant

PHP does have all sorts of problems as mentioned above, but the PHP community and PHP developers have been working on it. However, there are ignorant people who have never really understood PHP or even used it, and it is frustrating to conclude that PHP is a bad language just based on the comments on some community forums. Even one of my older mobile colleagues still thinks that the variable name in PHP is var.

Norm or norm

There are no rules, there is no circle, the society is like this, the team is like this, and the project is like this.

From a very young age, our parents began to teach us what we could and could not do. For example, "wash your hands before eating" and "don't make loud noises in public". When we enter the school and even enter the society, we understand that there are always various rules and regulations that bind us, whether it is organizational, moral, or legal. If we want to be a person who is respected by others and recognized by society, we must adhere to these norms.

There is no such thing as perfection in the world, and even the best norms are not perfect. Good norms can reduce the cost of collaboration between people, but at the same time, it will hinder flexibility, and how to grasp the degree of normative constraints is worth scrutinizing.

Before the PSR specification, there was no unified standard for code naming, file naming, and automatic loading, and each project was self-specifying or in a non-normative state. Later, PHPFIG developed the PSR specification in order to enable interoperability of components and to provide specifications for best programming and testing practices. The members of PHPFIG include many well-known open source project authors, such as CakePHP authors, Composer authors, Drupal authors, Phalcon authors, Symfony authors, Yii authors, etc. PSR is not an official specification, but many well-known open source project authors have been involved in developing the de facto specification that has made it a PHP project.

There are currently 9 implemented specifications for PSR specifications, 8 specifications in the draft stage, and 1 specification for deprecation, making a total of 18 specifications. Here are the specifications in alphabetical order:

PSR-0 Autoload Specification (Deprecated)
PSR-1 Basic Coding Specification (Implemented)
PSR-2 Coding Style Guide (Implemented)
PSR-3 Logging Interface (Implemented)
PSR-4 Autoload Specification (Implemented)
PSR-5 PHPDOC标准（草案）
PSR-6 Cache Interface (Implemented)
PSR-7 HTTP Message Interface (Implemented)
PSR-8 Hug Interface (Draft)
PSR-9 Security Notice (Draft)
PSR-10 Safety Reporting Process (Draft)
PSR-11 Container Interface (Implemented)
PSR-12 Extended Coding Style Guide (Draft)
PSR-13 Hypermedia Link (Implemented)
PSR-14 Event Manager (Draft)
PSR-15 HTTP中间件（草案）
PSR-16 Simple Caching (Implemented)
PSR-17 HTTP工厂 (草案)

Due to space limitations, only the implemented norms will be covered

Specifications that have been implemented

PSR-1 Basic Coding Specification

PSR-1 only regulates files, classes, and methods.

The file must only use <?php or <?=
The file must be without BOMUTF-8 encoding
The file should not be used to declare classes, methods, constants, etc., or to generate output, change .ini settings, etc
Namespaces and classes must comply with PSR-4 (PSR-0 is deprecated)
The naming format of the class name must be a large hump, e.g. MyClass
The name format of the constant must be uppercase + underscore link, for example, MY_CONSTANTS
The method must be named in a small hump format, e.g. myFunction

PSR-2 Coding Style Guide

PSR-2 is an extension of PSR-1 by regulating indentation, character limits, spaces, blank lines, and the visibility of classes and methods.

The code must comply with the PSR-1 specification
The indentation must be four spaces, not TAB
There is no hard limit on the number of characters on a line, but there is a soft limit of 120 characters. It is recommended to be less than 80 characters.
A blank line must be inserted after each namespace namespace declaration and use declaration block. Here are some examples:

namespace Vendor\Package;

use FooInterface;
use BarClass as Bar;
use OtherVendor\OtherPackage\BazClass;

The opening curly brace of the class must also be written on its own line after the function declaration, and the closing curly brace must also be written on its own line after the body of the function. Here are some examples:

//class declare
class Foo 
{
	//class body 
}

The opening curly brace of the method {must be on its own line after the method declaration, and the closing curly brace} must also be written on its own line after the body of the method. Here are some examples:

class Foo 
{
	//method declare
    public function sampleMethod($a, $b = null)
    {
		//method body
    }
    
}

The properties and methods of the class must be declared before the access modifier (private, protected, and public), abstract and final must be declared before the access modifier, and static must be declared after the access modifier. Here are some examples:

<?php
class Foo 
{
	//属性前必须添加修饰符(private,protected,public)
	private $sampleProperty; 
	
	//方法前必须添加修饰符(private,protected,public)
    public function sampleMethod($a, $b = null)
    {
    }
	
	//abstract必须在访问修饰符前面
	abstract public function sampleAbstractMethod();
	
	//static必须声明在访问修饰符后面
    final public static function sampleFinalStaticMethod()
    {
    }
}

There must be a space after the keyword that controls the structure, and it must not be when a method or function is called. Here are some examples:
The opening curly brace for the control structure must be written on the same line as the declaration, and the closing curly brace must be written on its own line after the body. Here are some examples:
There must be no spaces before the opening (after and closing closing parentheses) of the control structure. Here are some examples:

class Foo
{
    public function sampleMethod($a, $b = null)
    {
        if ($a === $b) {
            bar();
        } elseif ($a > $b) {
            $foo->bar($arg1);
        } else {
            BazClass::bar($arg2, $arg3);
        }
    }

PSR-3 log interface

PSR-3 defines a generic logging interface, which allows the logging library to log information by receiving a Psr\Log\LoggerInterface object in a simple and generic way.

Implemented the class library of the PSR-3 specification

monologue

PSR-4 auto-load specification

PSR-4 defines a specification for the automatic loading of corresponding classes by file paths.

The term "class" here refers to all class classes, interfaces, traits reusable code blocks, and other similar structures.
A complete class name needs to be <命名空间名><子命名空间名>in the format *\<类名>. The full class name must have a top-level namespace, called a "vendor namespace", the full class name can have one or more sub-namespaces, the full class name must have a final class name, the descending line in any part of the complete class name has no special meaning, the complete class name can be composed of arbitrary uppercase and lowercase letters, and all class names must be case-sensitive
When loading a file with a complete class name, remove the first namespace separator, and use one or more successive namespaces and sub-namespaces as the "namespace prefix", which must correspond to at least one "file base directory", and the sub-namespace after the namespace prefix must match the corresponding "file base directory", where the namespace separator will be used as the directory separator, and the class name at the end of the separator must be the corresponding .php Implementations of autoloaders with the same name as files with suffixes must not throw exceptions, trigger error messages at any level, and have no return value

example

The following table shows the file paths corresponding to the full class name, namespace prefix, and file base directory that meet the specification.

Full class name	Namespace prefix	Base directory	File path
\Acme\Log\Writer\File_Writer	Acme\Log\Writer	./acme-log-writer/lib/	./acme-log-writer/lib/File_Writer.php
\Aura\Web\Response\Status	Aura\Web	/path/to/aura-web/src/	/path/to/aura-web/src/Response/Status.php
\Symfony\Core\Request	Symfony\Core	./vendor/Symfony/Core/	./vendor/Symfony/Core/Request.php
\Zend\Acl	Zend	/usr/includes/Zend/	/usr/includes/Zend/Acl.php

For the implementation of this specification, please refer to relevant examples

PSR-6 cache interface

Caching is a common way to improve the performance of a project, and it is also a regular feature of most frameworks or libraries. This results in different frameworks or class inventories at different levels for caching solutions. This discrepancy forces developers to learn multiple systems that don't even provide them with the functionality they need. In addition, developers of caching libraries are faced with a choice: whether to support only a few frameworks, or to write a large number of adapters to adapt to a wide variety of systems.

PSR-6 will solve this problem, and library and framework developers can count on the caching system to work as intended, while the developer of the caching system will only need to implement a set of interfaces, rather than a full adapter.

PSR-7 HTTP消息接口

HTTP messages are the foundation of web development. Web browsers and HTTP clients such as cURL create HTTP request messages that are sent to the web server, which provides HTTP response messages. The server-side code receives the HTTP request message and returns an HTTP response message.

HTTP messages are often abstracted from the end user, but as developers, we often need to know how they are constructed and how to access or manipulate them to perform our tasks, whether it's for HTTP API requests, or for handling incoming requests.

Each HTTP request message has a specific form:

POST /path HTTP/1.1
Host: example.com

foo=bar&baz=bat

The first line of the request body is the "request line", which contains the HTTP request method, the HTTP request destination address (usually an absolute URL or the path of the web server), and the HTTP protocol version number. Next is one or more HTTP headers, a blank line with the message content.

HTTP response content has a similar structure

HTTP/1.1 200 OK
Content-Type: text/plain

This is the response body

The first line is the "status line", which contains the HTTP protocol version number, the HTTP status code and a "reason phrase" describing the status code, similar to the request message, followed by one or more HTTP headers, and a blank line with the message content.

The PSR-7 specification is an abstraction of HTTP messages and the elements that make them up.

The class library of PSR-7 was implemented

guzzlehttp/psr7:
oscarotero/psr7-middlewares
zendframework/zend-diactoros

PSR-11 container interface

PSR-11 is a generic interface for dependency injection containers, designed to standardize frameworks or libraries to obtain objects and parameters through containers.

Implemented the class library of PSR-11

PHP-IN/PHP-DI

PSR-13 hypermedia link

WHETHER IT'S HTML CONTENT OR CONTENT IN DIFFERENT API FORMATS, HYPERMEDIA LINKS ARE INCREASINGLY BECOMING AN IMPORTANT PART OF THE WEB. However, there is no single universal hypermedia format, nor is there a universal way to represent links between formats.

PSR-13 is designed to provide PHP developers with a simple, versatile, and independent way to represent hypermedia links in a serialized format that is used independently. This, in turn, allows the system to serialize the response of hypermedia links into one or more wired formats, independent of the process of deciding what those links should be.

PSR-16 Simple Cache

PSR-16 is designed to standardize a simple but extensible interface for caching entries and cache drivers.

Too much of the pain of framing

Since there is a language war, it is also a matter of course that PHP has too many frameworks as a language focused on the web domain. Do you sometimes find it frustrating to learn a framework that you can't finish?

Let's take a look at the major frameworks (in descending order of Github Star)

Laravel

Laravel is one of the hottest frameworks in PHP languages out there. With elegance as the goal, it uses a lot of new features of PHP, an active community, and a rich ecological environment. The latest LTS Laravel 5.5 already requires that the environment must be at least php 7.0. It's arguably the most stylish framework in the PHP world.

Symfony

Symfony is Papa's framework, the most powerful PHP framework. Many well-known open source projects are based on Symfony, such as Laravel, Drupal, PHPBB. Symfony's componentization coupling is very small, and you can use a single component in your project.

CodeIgniter

CI is an old PHP framework, which is easy to use, and the documentation and cases are very rich. But it is not rich enough in terms of features, and does not support too many new PHP features.

Yii2

Yii2 is a full-stack MVC framework with very good performance and scalability.

Phalcon

Phalcon is the fastest MVC framework in the PHP world, developed in the form of a Zend Extension. However, because PHP development is too black box and difficult to develop, the Phalcon team has developed another language Zephir to write Phalcon, so you can try it.

Slim

Slim is a small and well-rounded framework, and it is highly recommended for beginners to research its source code. If you're writing a small project, Slim is very handy.

Cakephp

CakePHP is not used too many people in China, but this does not affect its status as an established framework.

Lumen

Lumen is a framework focused on building microservices architectures and API applications.

In addition to the above frameworks, there are also Brother Bird's Yaf, the domestic ThinkPHP and PHP's official Zend Framework are also relatively well-known.

Generic components

Request

Since it is an HTTP project, the Request component is definitely indispensable, which encapsulates the HTTP information of the request.