What is PHP?
PHP (recursive acronym for PHP: Hypertext Preprocessor) is a widely-used open source general-purpose scripting language that is especially suited for web development and can be embedded into HTML.
Instead of lots of commands to output HTML (as seen in C or Perl), PHP pages contain HTML with embedded code that does “something” (in this case, output “Hi, I’m a PHP script!”). The PHP code is enclosed in special start and end processing instructions that allow you to jump into and out of “PHP mode.”