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.
PHP generates the HTML page on the server side. When the HTML page arrives at the browser, PHP has done its job. There is no way for PHP to do something after it has rendered the HTML.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
echo "Hi, I'm a PHP script!";
PHP code are executed on the server, and the result is returned to the browser as plain HTML
PHP files have extension ".php"
PHP can generate dynamic page content
PHP can create, open, read, write, and close files on the server
PHP can collect form data
PHP can send and receive cookies
PHP can add, delete, modify data in your database
PHP can restrict users to access some pages on your website
PHP can encrypt data
With PHP you are not limited to output HTML. You can output images, PDF files, and even Flash movies. You can also output any text, such as XHTML and XML.
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 <?php and ?> that allow you to jump into and out of "PHP mode."
ini_set('memory_limit', '-1'); -put into a php script it sets to unlimited the maximum amount of memory in bytes that a script is allowed to allocate (the danger of this is bad code will eat up all your memory)
You can define timeout constraints within your PHP application as follows:
PHP also provides a 'set_time_limit' function for this purpose: