cookies and sessions

What Is a Persistent Cookie?

A persistent cookie is a cookie which is stored in a cookie file permanently on the browser's computer. By default, cookies are created as temporary cookies which stored only in the browser's memory. When the browser is closed, temporary cookies will be erased. You should decide when to use temporary cookies and when to use persistent cookies based on their differences:

• Temporary cookies can not be used for tracking long-term information.

• Persistent cookies can be used for tracking long-term information.

• Temporary cookies are safer because no programs other than the browser can access them.

• 
  

• Persistent cookies are less secure because users can open cookie files see the cookie values.

What does a special set of tags do in PHP?

The output is displayed directly to the browser.

How do you define a constant?

Via define() directive, like define ("MYCONSTANT", 100);

How To Write the FORM Tag Correctly for Uploading Files?

When users clicks the submit button, files specified in the will be transferred from the browser to the Web server. This transferring (uploading) process is controlled by a properly written tag as:

Note that you must specify METHOD as "post" and ENCTYPE as "multipart/form-data" in order for the uploading process to work. The following PHP code, called logo_upload.php, shows you a complete FORM tag for file uploading:

print("

." method=post enctype=multipart/form-data>\n");

print("Please submit an image file a Web site logo for"

." fyicenter.com:
\n");

print("
\n");

print("\n");

print("\n");

?>

What are the differences between require and include, include_once?

Answer 1:
require_once() and include_once() are both the functions to include and evaluate the specified file only once. If the specified file is included previous to the present call occurrence, it will not be done again.

But require() and include() will do it as many times they are asked to do.

Anwser 2:
The include_once() statement includes and evaluates the specified file during the execution of the script. This is a behavior similar to the include() statement, with the only difference being that if the code from a file has already been included, it will not be included again. The major difference between include() and require() is that in failure include() produces a warning message whereas require() produces a fatal errors.

Anwser 3:
All three are used to an include file into the current page.
If the file is not present, require(), calls a fatal error, while in include() does not.
The include_once() statement includes and evaluates the specified file during the execution of the script. This is a behavior similar to the include() statement, with the only difference being that if the code from a file has already been included, it will not be included again. It des not call a fatal error if file not exists. require_once() does the same as include_once(), but it calls a fatal error if file not exists.

Anwser 4:
File will not be included more than once. If we want to include a file once only and further calling of the file will be ignored then we have to use the PHP function include_once(). This will prevent problems with function redefinitions, variable value reassignments, etc.