What is PHP language and what is it used for?

PHP (foreign name: PHP: Hypertext Preprocessor, Chinese name: "Hypertext Preprocessor") is a general open source scripting language. The syntax absorbs the characteristics of C language, Java and Perl, which is easy to learn and widely used. It is mainly suitable for the field of Web development. PHP's unique syntax mixes C, Java, Perl, and PHP's own syntax. It can execute dynamic web pages faster than CGI or Perl. Compared with other programming languages, dynamic pages made with PHP embed programs into HTML (an application under the Standard Universal Markup Language) document for execution, and the execution efficiency is much higher than CGI that completely generates HTML tags; PHP can also execute compiled code. Compilation can achieve encryption and optimize code running, making the code run faster.
PHP was originally the abbreviation of Personal Home Page and has been officially renamed "PHP: Hypertext Preprocessor". Note that it is not the abbreviation of "Hypertext Preprocessor". This way of writing the name into the definition is called a recursive abbreviation. PHP was created by Rasmus Lerdorf in 1994. It started as a simple program written in Perl language that Rasmus Lerdorf made to maintain a personal web page. These tools are used to display Rasmus Lerdorf's resume and count web traffic. Later it was rewritten in C language, including access to the database. He integrated these programs with some form interpreters and called them PHP/FI. PHP/FI can be connected to the database to generate simple dynamic web programs.
In 1995, the first version was released as Personal Home Page Tools (PHP Tools). Lerdorf wrote some documents introducing this program. And PHP1.0 was released! In this version, simple functions such as guest book and visitor counter are provided. In the future, more and more websites use PHP, and there are strong requests to add some features. For example, loop statements, array variables, etc.; after new members joined the development team, Rasmus Lerdorf released PHP/FI to the public on June 8, 1995, hoping to speed up program development and find errors through the community. This released version, named PHP 2, already has some prototypes of PHP, such as Perl-like variable naming, form processing capabilities, and the ability to embed execution in HTML. The program syntax is also similar to Perl, with more restrictions, but it is simpler and more flexible. PHP/FI added support for MySQL, and has since established PHP's position in dynamic web development. By the end of 1996, there were 15,000 websites using PHP/FI.
ISAPI Filter
In 1997, two Israeli programmers working at Technion IIT: Zeev Suraski and Andi Gutmans, rewrote the PHP parser and became the basis of PHP 3. At this time, PHP was also renamed PHP: Hypertext Preprocessor. After several months of testing, the development team released PHP/FI 2 in November 1997. Then the open testing of PHP 3 began, and finally PHP 3 was officially released in June 1998. Zeev Suraski and Andi Gutmans began to rewrite the core of PHP after the release of PHP 3. The profiler released in 1999 was called Zend Engine. They also established Zend Technologies in Ramat Gan, Israel, to manage PHP development.
On May 22, 2000, PHP 4 based on Zend Engine 1.0 was officially released, and PHP 5 was released on July 13, 2004. PHP 5 used the second generation Zend Engine. PHP includes many new features, such as enhanced object-oriented functions, the introduction of PDO (PHP Data Objects, an extension function library for accessing databases), and many performance enhancements. PHP 4 will no longer be updated to encourage users to move to PHP 5.
In 2008, PHP 5 became the only PHP version under development. In the future, PHP 5.3 will add Late static binding and some other functional enhancements. The development of PHP 6 is also in progress. The main improvements include the removal of register_globals, magic quotes and Safe mode.
The latest stable version of PHP: 5.4.30 (2013.6.26)
The latest official version of PHP: 5.5.14 (2014.6.24)
The latest test version of PHP: 5.6.0 RC2 (2014.6.03 )
On June 20, 2013, the PHP development team is proud to announce the launch of PHP 5.5.0. This release contains a lot of new features and bug fixes. One thing that developers need to pay special attention to is that Windows XP and 2003 systems are no longer supported.
On October 16, 2014, the PHP development team announced that PHP 5.6.2 is available. Four security-related bugs are fixed in this release, including fixes for CVE-2014-3668, CVE-2014-3669 and CVE-2014-3670. All PHP 5.6 users are encouraged to upgrade to this version

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