MIME - Multi-purpose Internet Mail Extensions. 

MIME types represents a standard way of classifying file types over Internet. 

Web servers and browsers have a list of MIME types, which facilitates files transfer of the same type in the same way, irrespective of operating system they are working in.

A MIME type has two parts: a type and a subtype. They are separated by a slash (/). 

MIME type for Microsoft Word files is application and the subtype is msword, i.e. application/msword.

Notices, Warnings and Fatal errors are the types of errors in PHP

Notices: 

Notices represents non-critical errors, i.e. accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all but whenever required, you can change this default behavior.

Warnings: 

Warnings are more serious errors but they do not result in script termination. i.e calling include() a file which does not exist. By default, these errors are displayed to the user.

Fatal errors: 

Fatal errors are critical errors i.e. calling a non-existent function or class. These errors cause the immediate termination of the script.

$message is a variable with a fixed name. $$message is a variable whose name is stored in $message. 

If $message contains "var", $$message is the same as $var.

echo() and print() are language constructs in PHP, both are used to output strings. The speed of both statements is almost the same.

echo() can take multiple expressions whereas print cannot take multiple expressions.

Print return true or false based on success or failure whereas echo doesn't return true or false.

PEAR(PHP Extension and Application Repository) is a framework and repository for reusable PHP components. PEAR is a code repository containing all kinds of php code snippets and libraries. 

PEAR also offers a command-line interface that can be used to automatically install "packages".

PHP: Hypertext Preprocessor is open source server-side scripting language that is widely used for web development. PHP scripts are executed on the server. PHP allows writing dynamically generated web pages efficiently and quickly. The syntax is mostly borrowed from C, Java and perl. PHP is free to download and use.

- Create a template that designs a layout for your application.

- Create the composing pages.

- Create a definition which means that suppose that you configured Tiles, in web.xml, to startup using the TilesServlet, we need to specify which files will contain the Tiles definitions to load.

- Render the definition.

The interface org.apache.struts.upload.FormFile is used for the struts file upload application. This interface represents a file that has been uploaded by a client. It is the only interface or class in upload package which is typically referenced directly by a Struts application.

This is not specific to Struts in case of DHTML but the two things that are needed in DHTML page is: first, the form needs to specify an enctype of multipart/form-data and second an <input> form control of type file.

Following are the steps to load file in DHTML:

- Creating a bean

- Writing the ActionClass.

- Mapping the bean in struts-config.xml

- Defining actionmapping

- Developing the DHTML page.