$message is a simple variable whereas $$message is a reference variable. Example:
$user = ‘bob’
is equivalent to
$holder = ‘user’; $$holder = ‘bob’;
They are both variables. But $message is a variable with a fixed name. $$message is a variable who’s name is stored in $message. For example, if $message contains “var”, $$message is the same as $var.
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:
The output is displayed directly to the browser.
Via define() directive, like define (“MYCONSTANT”, 100);
When users clicks the submit button, files specified in the <INPUT TYPE=FILE…> will be transferred from the browser to the Web server. This transferring (uploading) process is controlled by a properly written <FORM…> tag as:
<FORM ACTION=receiving.php METHOD=post ENCTYPE=multipart/form-data>
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:
." method=post enctype=multipart/form-data>\n");
print("Please submit an image file a Web site logo for"
print("<input type=file name=fyicenter_logo><br>\n");