w3resource

Making libraries/packages installable using composer

Introduction

It may interest you to note that, that every project with a “composer.json” file in its directory is a library/package. Whenever we add the “require” key, we are making a package that will depend on other packages. The major difference between our projects and a standard package is that our projects are packages without names. Therefore, adding the name property  in our “composer.json” makes our project an installable package.

In the last tutorial, we installed and used classes from open source packages, in this tutorial, we will look at how to make our own libraries/project/packages installable using Composer. We will use the word library, package and project to refer to a package, just to make us better understand the concept.

#Package Name

For our library to be installable, we library must have a vendor and package name. We do this by adding these names in the “package.json” file as shown in the code snippet below.

{
	“name” : “vitalis/hello-world”
	“require”: {
	     “monolog/monolog”:”1.0.*”
          }
}

In the above code snippet, “vitalis” is the vendor name and “hello-word” is the package name. The vendor name, as explained in the previous tutorial helps in preventing name conflicts as a package can comfortable have the same package name, but different vendor name. These names are always case insensitive, but the conversion is to use lower cases and dashes for word separators.

#Package Versioning

In most of our development processes, we are likely to make use of Version Control Systems(VCS) like Git in our project. In such cases, we are not required to explicitly state the version of our project/package in the “composer.json” file as composer user VCS branches and tags to resolve the  version constraints.

But in a case when we are maintaining out the package by hand, we must explicitly state the version of our package or project in the “composer.json” file as shown in the code snippet below:

{
	“version” : “1.0.0”
}

It is important to note that adding a hard-coded version number to VCS, will result to version and tag conflicts as composer will not be able to resolve the version of our projects.

#Version by VCS

Composer makes use of our branch and tags to resolve the versions constraints of our project dependencies stated in our required fields. It also maps these versions to their right origins and saves them in the “composer.lock” file

#Publishing to VCS

To publish our package to a VCS repository, our project must contain a composer.json file, so in our case our project is already installable since it contains a ”composer.json” file.

In this tutorial, we will publish “vitalis/hello-world” library to GitHub under https://github.com/agavitalis/hello-world

Now to test our just published library, we will create a new project locally. We will call this project “vitalis/use-hello-world”. This locally created project will depend on “vitalis/hello-world”, which will turn depend on some other libraries, “monolog/monolog” in this case.

To accomplish this, “vitalis/use-hello-world” project must contain a composer.json file on which we will specify how to require the “vitalis/hello-world” hosted in GitHub. A sample specification of how the composer.json file of “vitalis/use-hello-world” project is shown in the code snippet below:

{
    "name": "vitalis/use-hello-world",
    "repositories": {
        "type ": "vcs ",
        “url” : “https://github.com/agavitalis/hello-world”
    }
    "require": {
        "vitalis/hello-composer": "dev-master"
    }
}

The above code snippet shows the content of the “composer.json” file of our locally created “vitalis/use-hello-world” project. We may skip the name option if we don’t have the intention of publishing this project, but we included it for clarity purposes.

The repositories specifications were added to tell the composer where to locate the vitalis/hello-world package .

At this point we can run the “composer install” command, and composer will grab our “vitalis/hello-world” package into the “vitalis/use-hello-world” vendor folder.

#Publishing to Packagist

So far, we can now publish packages, but having to include the VCS details for each package is rather redundant and tiresome, and we will not like to that, thus Packagist.

Packagist is a central repository for composer and it comes enabled by default. Any package published in Packagist is automatically accessible through composer, that was why we were able to specify “monolog/monolog” in the “vitalis/hello-world” package without specifying its repository.

So, to share our vitalis/monolog package to the world, we simply visit https://packagist.org and hit the submit button. This will prompt us to register if we are not yet registered, and it will then allow us to submit the URL to our VCS repository. Once we have done this, our project is live to the world, and it could be installed at one click using composer without having to specify the repository.

Yes, we have successfully gone through the processes of making our libraries installable using composer. In the next tutorials, we will follow these processes and create an actual package, make it live in Packagist, and then consume the package in another project.

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PHP: Tips of the Day

How do you parse and process HTML/XML in PHP?

Native XML Extensions

I prefer using one of the native XML extensions since they come bundled with PHP, are usually faster than all the 3rd party libs and give me all the control I need over the markup.

DOM

The DOM extension allows you to operate on XML documents through the DOM API with PHP 5. It is an implementation of the W3C's Document Object Model Core Level 3, a platform- and language-neutral interface that allows programs and scripts to dynamically access and update the content, structure and style of documents.

DOM is capable of parsing and modifying real world (broken) HTML and it can do XPath queries. It is based on libxml.

It takes some time to get productive with DOM, but that time is well worth it IMO. Since DOM is a language-agnostic interface, you'll find implementations in many languages, so if you need to change your programming language, chances are you will already know how to use that language's DOM API then.

A basic usage example can be found in Grabbing the href attribute of an A element and a general conceptual overview can be found at DOMDocument in php

How to use the DOM extension has been covered extensively on StackOverflow, so if you choose to use it, you can be sure most of the issues you run into can be solved by searching/browsing Stack Overflow.

XMLReader

The XMLReader extension is an XML pull parser. The reader acts as a cursor going forward on the document stream and stopping at each node on the way.

XMLReader, like DOM, is based on libxml. I am not aware of how to trigger the HTML Parser Module, so chances are using XMLReader for parsing broken HTML might be less robust than using DOM where you can explicitly tell it to use libxml's HTML Parser Module.

A basic usage example can be found at getting all values from h1 tags using php

XML Parser

This extension lets you create XML parsers and then define handlers for different XML events. Each XML parser also has a few parameters you can adjust.

The XML Parser library is also based on libxml, and implements a SAX style XML push parser. It may be a better choice for memory management than DOM or SimpleXML, but will be more difficult to work with than the pull parser implemented by XMLReader.

SimpleXml

The SimpleXML extension provides a very simple and easily usable toolset to convert XML to an object that can be processed with normal property selectors and array iterators.

SimpleXML is an option when you know the HTML is valid XHTML. If you need to parse broken HTML, don't even consider SimpleXml because it will choke.

A basic usage example can be found at A simple program to CRUD node and node values of xml file and there is lots of additional examples in the PHP Manual.

3rd Party Libraries (libxml based)

If you prefer to use a 3rd-party lib, I'd suggest using a lib that actually uses DOM/libxml underneath instead of string parsing.

FluentDom Repo

FluentDOM provides a jQuery-like fluent XML interface for the DOMDocument in PHP. Selectors are written in XPath or CSS (using a CSS to XPath converter). Current versions extend the DOM implementing standard interfaces and add features from the DOM Living Standard. FluentDOM can load formats like JSON, CSV, JsonML, RabbitFish and others. Can be installed via Composer.

HtmlPageDom

Wa72\HtmlPageDom` is a PHP library for easy manipulation of HTML documents using It requires DomCrawler from Symfony2 components for traversing the DOM tree and extends it by adding methods for manipulating the DOM tree of HTML documents.

phpQuery (not updated for years)

phpQuery is a server-side, chainable, CSS3 selector driven Document Object Model (DOM) API based on jQuery JavaScript Library written in PHP5 and provides additional Command Line Interface (CLI).

Zend_Dom

Zend_Dom provides tools for working with DOM documents and structures. Currently, we offer Zend_Dom_Query, which provides a unified interface for querying DOM documents utilizing both XPath and CSS selectors.

QueryPath

QueryPath is a PHP library for manipulating XML and HTML. It is designed to work not only with local files, but also with web services and database resources. It implements much of the jQuery interface (including CSS-style selectors), but it is heavily tuned for server-side use. Can be installed via Composer.

fDOMDocument

fDOMDocument extends the standard DOM to use exceptions at all occasions of errors instead of PHP warnings or notices. They also add various custom methods and shortcuts for convenience and to simplify the usage of DOM.

sabre/xml

sabre/xml is a library that wraps and extends the XMLReader and XMLWriter classes to create a simple "xml to object/array" mapping system and design pattern. Writing and reading XML is single-pass and can therefore be fast and require low memory on large xml files.

FluidXML

FluidXML is a PHP library for manipulating XML with a concise and fluent API. It leverages XPath and the fluent programming pattern to be fun and effective.

3rd-Party (not libxml-based)

The benefit of building upon DOM/libxml is that you get good performance out of the box because you are based on a native extension. However, not all 3rd-party libs go down this route. Some of them listed below

PHP Simple HTML DOM Parser

  • An HTML DOM parser written in PHP5+ lets you manipulate HTML in a very easy way!
  • Require PHP 5+.
  • Supports invalid HTML.
  • Find tags on an HTML page with selectors just like jQuery.
  • Extract contents from HTML in a single line.

I generally do not recommend this parser. The codebase is horrible and the parser itself is rather slow and memory hungry. Not all jQuery Selectors (such as child selectors) are possible. Any of the libxml based libraries should outperform this easily.

PHP Html Parser

PHPHtmlParser is a simple, flexible, html parser which allows you to select tags using any css selector, like jQuery. The goal is to assiste in the development of tools which require a quick, easy way to scrap html, whether it's valid or not! This project was original supported by sunra/php-simple-html-dom-parser but the support seems to have stopped so this project is my adaptation of his previous work.

Again, I would not recommend this parser. It is rather slow with high CPU usage. There is also no function to clear memory of created DOM objects. These problems scale particularly with nested loops. The documentation itself is inaccurate and misspelled, with no responses to fixes since 14 Apr 16.

Ganon

  • A universal tokenizer and HTML/XML/RSS DOM Parser
    • Ability to manipulate elements and their attributes
    • Supports invalid HTML and UTF8
  • Can perform advanced CSS3-like queries on elements (like jQuery -- namespaces supported)
  • A HTML beautifier (like HTML Tidy)
    • Minify CSS and Javascript
    • Sort attributes, change character case, correct indentation, etc.
  • Extensible
    • Parsing documents using callbacks based on current character/token
    • Operations separated in smaller functions for easy overriding
  • Fast and Easy

Never used it. Can't tell if it's any good.

HTML 5

You can use the above for parsing HTML5, but there can be quirks due to the markup HTML5 allows. So for HTML5 you want to consider using a dedicated parser, like

html5lib

A Python and PHP implementations of a HTML parser based on the WHATWG HTML5 specification for maximum compatibility with major desktop web browsers.

We might see more dedicated parsers once HTML5 is finalized. There is also a blogpost by the W3's titled How-To for html 5 parsing that is worth checking out.

WebServices

If you don't feel like programming PHP, you can also use Web services. In general, I found very little utility for these, but that's just me and my use cases.

ScraperWiki.

ScraperWiki's external interface allows you to extract data in the form you want for use on the web or in your own applications. You can also extract information about the state of any scraper.

Regular Expressions

Last and least recommended, you can extract data from HTML with regular expressions. In general using Regular Expressions on HTML is discouraged.

Most of the snippets you will find on the web to match markup are brittle. In most cases they are only working for a very particular piece of HTML. Tiny markup changes, like adding whitespace somewhere, or adding, or changing attributes in a tag, can make the RegEx fails when it's not properly written. You should know what you are doing before using RegEx on HTML.

HTML parsers already know the syntactical rules of HTML. Regular expressions have to be taught for each new RegEx you write. RegEx are fine in some cases, but it really depends on your use-case.

You can write more reliable parsers, but writing a complete and reliable custom parser with regular expressions is a waste of time when the aforementioned libraries already exist and do a much better job on this.

Ref : https://bit.ly/2VdyKBy