What is PHP?
PHP: Hypertext Preprocessor (or simply PHP) is a general-purpose programming language originally designed for web development. It was originally created by Rasmus Lerdorfin 1994; the PHP reference implementation is now produced by The PHP Group. PHP originally stood for Personal Home Page, but it now stands for the recursive initialismPHP: Hypertext Preprocessor.
PHP code may be executed with a command line interface (CLI), embedded into HTML code, or used in combination with various web template systems, web content management systems, and web frameworks. PHP code is usually processed by a PHP interpreter implemented as a module in a web server or as a Common Gateway Interface (CGI) executable. The web server outputs the results of the interpreted and executed PHP code, which may be any type of data, such as generated HTML code or binary image data. PHP can be used for many programming tasks outside of the web context, such as standalone graphical applications and robotic drone control.
The standard PHP interpreter, powered by the Zend Engine, is free software released under the PHP License. PHP has been widely ported and can be deployed on most web servers on almost every operating system and platform, free of charge.
The PHP language evolved without a written formal specification or standard until 2014, with the original implementation acting as the de facto standard which other implementations aimed to follow. Since 2014, work has gone on to create a formal PHP specification.
As of August 2019, the majority of sites on the web using PHP are still on version 5.6 or older; versions prior to 7.1 are no longer officially supported by The PHP Development Team, but security support is provided for longer by third parties, such as Debian.
PHP development began in 1994 when Rasmus Lerdorf wrote several Common Gateway Interface (CGI) programs in C, which he used to maintain his personal homepage. He extended them to work with web forms and to communicate with databases, and called this implementation "Personal Home Page/Forms Interpreter" or PHP/FI.
PHP/FI could be used to build simple, dynamic web applications. To accelerate bug reporting and improve the code, Lerdorf initially announced the release of PHP/FI as "Personal Home Page Tools (PHP Tools) version 1.0" on the Usenet discussion group comp.infosystems.www.authoring.cgi on June 8, 1995. This release already had the basic functionality that PHP has today. This included Perl-like variables, form handling, and the ability to embed HTML. The syntax resembled that of Perl, but was simpler, more limited and less consistent.
Early PHP was not intended to be a new programming language, and grew organically, with Lerdorf noting in retrospect: "I don't know how to stop it, there was never any intent to write a programming language [...] I have absolutely no idea how to write a programming language, I just kept adding the next logical step on the way." A development team began to form and, after months of work and beta testing, officially released PHP/FI 2 in November 1997.
The fact that PHP was not originally designed, but instead was developed organically has led to inconsistent naming of functions and inconsistent ordering of their parameters. In some cases, the function names were chosen to match the lower-level libraries which PHP was "wrapping", while in some very early versions of PHP the length of the function names was used internally as a hash function, so names were chosen to improve the distribution of hash values.
PHP 3 and 4
Zeev Suraski and Andi Gutmans rewrote the parser in 1997 and formed the base of PHP 3, changing the language's name to the recursive acronym PHP: Hypertext Preprocessor.Afterwards, public testing of PHP 3 began, and the official launch came in June 1998. Suraski and Gutmans then started a new rewrite of PHP's core, producing the Zend Engine in 1999. They also founded Zend Technologies in Ramat Gan, Israel.
On May 22, 2000, PHP 4, powered by the Zend Engine 1.0, was released. As of August 2008 this branch reached version 4.4.9. PHP 4 is no longer under development nor will any security updates be released.
On July 14, 2004, PHP 5 was released, powered by the new Zend Engine II. PHP 5 included new features such as improved support for object-oriented programming, the PHP Data Objects (PDO) extension (which defines a lightweight and consistent interface for accessing databases), and numerous performance enhancements. In 2008, PHP 5 became the only stable version under development. Late static binding had been missing from PHP and was added in version 5.3.
Many high-profile open-source projects ceased to support PHP 4 in new code as of February 5, 2008, because of the GoPHP5 initiative, provided by a consortium of PHP developers promoting the transition from PHP 4 to PHP 5.
Over time, PHP interpreters became available on most existing 32-bit and 64-bit operating systems, either by building them from the PHP source code, or by using pre-built binaries. For PHP versions 5.3 and 5.4, the only available Microsoft Windows binary distributions were 32-bit IA-32 builds, requiring Windows 32-bit compatibility mode while using Internet Information Services (IIS) on a 64-bit Windows platform. PHP version 5.5 made the 64-bit x86-64 builds available for Microsoft Windows.
Official security support for PHP 5.6 ended on 31 December 2018, but Debian 8.0 Jessie will extend support until June 2020.
PHP 6 and Unicode
PHP received mixed reviews due to lacking native Unicode support at the core language level. In 2005, a project headed by Andrei Zmievski was initiated to bring native Unicode support throughout PHP, by embedding the International Components for Unicode (ICU) library, and representing text strings as UTF-16 internally. Since this would cause major changes both to the internals of the language and to user code, it was planned to release this as version 6.0 of the language, along with other major features then in development.
However, a shortage of developers who understood the necessary changes, and performance problems arising from conversion to and from UTF-16, which is rarely used in a web context, led to delays in the project. As a result, a PHP 5.3 release was created in 2009, with many non-Unicode features back-ported from PHP 6, notably namespaces. In March 2010, the project in its current form was officially abandoned, and a PHP 5.4 release was prepared containing most remaining non-Unicode features from PHP 6, such as traits and closure re-binding. Initial hopes were that a new plan would be formed for Unicode integration, but as of 2014 none had been adopted.
During 2014 and 2015, a new major PHP version was developed, which was numbered PHP 7. The numbering of this version involved some debate. While the PHP 6 Unicode experiment had never been released, several articles and book titles referenced the PHP 6 name, which might have caused confusion if a new release were to reuse the name. After a vote, the name PHP 7 was chosen.
The foundation of PHP 7 is a PHP branch that was originally dubbed PHP next generation (phpng). It was authored by Dmitry Stogov, Xinchen Hui and Nikita Popov, and aimed to optimize PHP performance by refactoring the Zend Engine while retaining near-complete language compatibility. As of 14 July 2014, WordPress-based benchmarks, which served as the main benchmark suite for the phpng project, showed an almost 100% increase in performance. Changes from phpng are also expected to make it easier to improve performance in the future, as more compact data structures and other changes are seen as better suited for a successful migration to a just-in-time (JIT) compiler. Because of the significant changes, the reworked Zend Engine is called Zend Engine 3, succeeding Zend Engine 2 used in PHP 5.
Because of major internal changes in phpng it must receive a new major version number of PHP, rather than a minor PHP 5 release, according to PHP's release process. Major versions of PHP are allowed to break backward-compatibility of code and therefore PHP 7 presented an opportunity for other improvements beyond phpng that require backward-compatibility breaks. In particular, it involved the following changes:
- Many fatal- or recoverable-level legacy PHP error mechanisms were replaced with modern object-oriented exceptions.
- The syntax for variable dereferencing was reworked to be internally more consistent and complete, allowing the use of the operators
::, with arbitrary meaningful left-side expressions.
- Support for legacy PHP 4-style constructor methods was deprecated.
- The behavior of the
foreachstatement was changed to be more predictable.
- Constructors for the few classes built-in to PHP which returned null upon failure were changed to throw an exception instead, for consistency.
- Several unmaintained or deprecated server application programming interfaces (SAPIs) and extensions were removed from the PHP core, most notably the legacy
- The behavior of the
list()operator was changed to remove support for strings.
- Support was removed for legacy ASP-style delimiters
<% and %> and <script language="php"> ... </script>
- An oversight allowing a switch statement to have multiple
defaultclauses was fixed
- Support for hexadecimal number support in some implicit conversions from strings to number types was removed.
- The left-shift and right-shift operators were changed to behave more consistently across platforms.
- Conversions between integers and floating point numbers were tightened and implemented more consistently across platforms.
PHP 7 also included new language features. Most notably, it introduces return type declarations for functions which complement the existing parameter type declarations, and support for the scalar types (integer, float, string, and boolean) in parameter and return type declarations.
The following "Hello, World!" program is written in PHP code embedded in an HTML document:
<!DOCTYPE html> <title>PHP "Hello, World!" program</title> <?php echo '<p>Hello World</p>'; ?>
However, as no requirement exists for PHP code to be embedded in HTML, the simplest version of Hello, World! may be written like this, with the closing tag omitted as preferred in files containing pure PHP code.
As well, there is no requirement that a PHP file contain PHP code at all – the interpreter will output data outside of PHP tags unchanged so a simple text file containing "
Hello world" will give the same output.
The PHP interpreter only executes PHP code within its delimiters. Anything outside its delimiters is not processed by PHP, although non-PHP text is still subject to control structures described in PHP code. The most common delimiters are
<?php to open and
?> to close PHP sections. The shortened form
<? also exists. This short delimiter makes script files less portable, since support for them can be disabled in the local PHP configuration and it is therefore discouraged; there is no recommendation against the echo short tag
<?=. Prior to PHP 5.4.0, this short syntax for
echo() only works with the
The first form of delimiters,
?>, in XHTML and other XML documents, creates correctly formed XML processing instructions. This means that the resulting mixture of PHP code and other markup in the server-side file is itself well-formed XML.
Variables are prefixed with a dollar symbol, and a type does not need to be specified in advance. PHP 5 introduced type hinting that allows functions to force their parameters to be objects of a specific class, arrays, interfaces or callback functions. However, before PHP 7.0, type hints could not be used with scalar types such as integer or string.
Unlike function and class names, variable names are case sensitive. Both double-quoted ("") and heredoc strings provide the ability to interpolate a variable's value into the string. PHP treats newlines as whitespace in the manner of a free-form language, and statements are terminated by a semicolon. PHP has three types of comment syntax:
/* */ marks block and inline comments;
# are used for one-line comments. The
echo statement is one of several facilities PHP provides to output text.
In terms of keywords and language syntax, PHP is similar to the C style syntax.
while loops, and function returns are similar in syntax to languages such as C, C++, C#, Java and Perl.
Laravel Introduction With Video
Laravel is a free, open-source PHP web framework, created by Taylor Otwell and intended for the development of web applications following the model–view–controller (MVC) architectural pattern and based on Symfony. Some of the features of Laravel are a modular packaging system with a dedicated dependency manager, different ways for accessing relational databases, utilities that aid in application deployment and maintenance, and its orientation toward syntactic sugar
Taylor Otwell created Laravel as an attempt to provide a more advanced alternative to the CodeIgniter framework, which did not provide certain features such as built-in support for user authentication and authorization. Laravel's first beta release was made available on June 9, 2011, followed by the Laravel 1 release later in the same month. Laravel 1 included built-in support for authentication, localisation, models, views, sessions, routing and other mechanisms, but lacked support for controllers that prevented it from being a true MVC framework.
Laravel 2 was released in September 2011, bringing various improvements from the author and community. Major new features included the support for controllers, which made Laravel 2 a fully MVC-compliant framework, built-in support for the inversion of control (IoC) principle, and a templating system called Blade. As a downside, support for third-party packages was removed in Laravel 2.
Laravel 3 was released in February 2012 with a set of new features including the command-line interface (CLI) named Artisan, built-in support for more database management systems, database migrations as a form of version control for database layouts, support for handling events, and a packaging system called Bundles. An increase of Laravel's userbase and popularity lined up with the release of Laravel 3.
Laravel 4, codenamed Illuminate, was released in May 2013. It was made as a complete rewrite of the Laravel framework, migrating its layout into a set of separate packages distributed through Composer, which serves as an application-level package manager. Such a layout improved the extensibility of Laravel 4, which was paired with its official regular release schedule spanning six months between minor point releases. Other new features in the Laravel 4 release include database seeding for the initial population of databases, support for message queues, built-in support for sending different types of email, and support for delayed deletion of database records called soft deletion.
Laravel 5 was released in February 2015 as a result of internal changes that ended up in renumbering the then-future Laravel 4.3 release. New features in the Laravel 5 release include support for scheduling periodically executed tasks through a package called Scheduler, an abstraction layer called Flysystem that allows remote storage to be used in the same way as local file systems, improved handling of package assets through Elixir, and simplified externally handled authentication through the optional Socialite package. Laravel 5 also introduced a new internal directory tree structure for developed applications.
In March 2015, a SitePoint survey listed Laravel as the most popular PHP framework.
Laravel 5.1, released in June 2015, was the first release of Laravel to receive long-term support (LTS). New LTS versions were planned for one every two years.
Laravel 5.3 was released on August 23, 2016. The new features in 5.3 are focused on improving developer speed by adding additional out of the box improvements for common tasks.
Laravel 5.4 was released on January 24, 2017, with many new features like Laravel Dusk, Laravel Mix, Blade Components and Slots, Markdown Emails, Automatic Facades, Route Improvements, Higher Order Messaging for Collections, and many others.
Laravel 5.5 was released on August 30, 2017.
Laravel 5.6 was released on February 7, 2018.
Laravel 5.7 was released on September 4, 2018.
Laravel 5.8 was released on February 26, 2019.
The following features serve as Laravel's key design points (where not specifically noted, descriptions refer to the features of Laravel 3)
- Bundles provide a modular packaging system since the release of Laravel 3, with bundled features already available for easy addition to applications. Furthermore, Laravel 4 uses Composer as a dependency manager to add framework-agnostic and Laravel-specific PHP packages available from the Packagist repository.
- Eloquent ORM (object-relational mapping) is an advanced PHP implementation of the active record pattern, providing at the same time internal methods for enforcing constraints on the relationships between databaseobjects. Following the active record pattern, Eloquent ORM presents database tables as classes, with their object instances tied to single table rows.
- Query builder, available since Laravel 3, provides a more direct database access alternative to the Eloquent ORM. Instead of requiring SQL queries to be written directly, Laravel's query builder provides a set of classes and methods capable of building queries programmatically. It also allows selectable caching of the results of executed queries.
- Application logic is an integral part of developed applications, implemented either by using controllers or as part of the route declarations. The syntax used to define application logic is similar to the one used by Sinatraframework.
- Reverse routing defines a relationship between the links and routes, making it possible for later changes to routes to be automatically propagated into relevant links. When the links are created by using names of existing routes, the appropriate uniform resource identifiers (URIs) are automatically created by Laravel.
- Restful controllers provide an optional way for separating the logic behind serving HTTP GET and POST requests.
- Class auto loading provides automated loading of PHP classes without the need for manual maintenance of inclusion paths. On-demand loading prevents inclusion of unnecessary components, so only the actually used components are loaded.
- View composers serve as customizable logical code units that can be executed when a view is loaded.
- Blade templating engine combines one or more templates with a data model to produce resulting views, doing that by transpiling the templates into cached PHP code for improved performance. Blade also provides a set of its own control structures such as conditional statements and loops, which are internally mapped to their PHP counterparts. Furthermore, Laravel services may be called from Blade templates, and the templating engine itself can be extended with custom directives.
- IoC containers make it possible for new objects to be generated by following the inversion of control (IoC) principle, in which the framework calls into the application- or task-specific code, with optional instantiating and referencing of new objects as singletons.
- Migrations provide a version control system for database schemas, making it possible to associate changes in the application's codebase and required changes in the database layout. As a result, this feature simplifies the deployment and updating of Laravel-based applications.
- Database seeding provides a way to populate database tables with selected default data that can be used for application testing or be performed as part of the initial application setup.
- Unit testing is provided as an integral part of Laravel,:61–62 which itself contains unit tests that detect and prevent regressions in the framework. Unit tests can be run through the provided artisan command-line utility.
- Automatic pagination simplifies the task of implementing pagination, replacing the usual manual implementation approaches with automated methods integrated into Laravel.
- Form request is a feature of Laravel 5 that serves as the base for form input validation by internally binding event listeners, resulting in automated invoking of the form validation methods and generation of the actual form.
- Homestead - a Vagrant virtual machine that provides Laravel developers with all the tools necessary to develop Laravel straight out of the box, including, Ubuntu, Gulp, Bower and other development tools that are useful in developing full scale web applications.
Ready-to-use packages provided by Laravel through Composer and Packagist include the following:
Cashier, introduced in Laravel 4.2, provides an interface for managing subscription billing services provided by Stripe, such as handling coupons and generating invoices.
- SSH, introduced in Laravel 4.1, allows programmatic execution of CLI commands on remote servers using the Secure Shell (SSH) as an encrypted network protocol.
- Scheduler, introduced in Laravel 5.0, is an addition to the Artisan command-line utility that allows programmatic scheduling of periodically executed tasks. Internally, Scheduler relies on the cron daemon to run a single Artisan job that, in turn, executes the configured tasks.
- Flysystem, introduced in Laravel 5.0, is a file system abstraction layer that allows local file systems and cloud-based storage services provided by Amazon S3 and Rackspace Cloud to be used transparently and in the same way.
- Socialite, introduced in Laravel 5.0 as an optional package, provides simplified mechanisms for authentication with different OAuth providers, including Facebook, Twitter, Google, GitHub and Bitbucket.
In addition to Laravel's built-in and optional packages, Laravel also offers a paid set of additional tools and services.
Laravel Spark was developed by Taylor Otwell and provides additional tools for online SaaS businesses to integrate with services like Stripe, producing invoices, Bootstrap 4.0, and team authentication. As of February 2019, the package version is 8.0.
Laravel also offers Laravel Forge, to provision and deploy unlimited PHP applications on DigitalOcean, Linode, AWS, and more. Its features consists of managing SSL certificates, cron jobs, queues, load balancers, and more.
Laravel's command-line interface (CLI), called Artisan, was initially introduced in Laravel 3 with a limited set of capabilities. Laravel's later migration to a Composer-based architecture allowed Artisan to incorporate different components from the Symfony framework, resulting in the availability of additional Artisan features in Laravel 4.
The features of Artisan are mapped to different subcommands of the Artisan command-line utility, providing functionality that aids in managing and building Laravel-based applications. Common uses of Artisan include managing database migrations and seeding, publishing package assets, and generating boilerplate code for new controllers and migrations; the latter frees the developer from creating proper code skeletons. The functionality and capabilities of Artisan can also be expanded by implementing new custom commands, which, for example, may be used to automate application-specific recurring tasks.