PHP is a scripting language used to extend the capabilities of web pages. PHP does not usually have to worry about the correctness of the variable types, memory allocation for them, etc.
To file has been recognized by the Web server as a PHP script must have the appropriate extension. usually .php3 php or php4. After the granting of such an extension to the file server you will know that the file is not intended for direct display, but that first you have to pass by the PHP parser.
Example Script Hello World
echo ‘Hello World’;
First you must save the file with the appropriate extension and put it place (that is, the directory from which you access will have a web server). After entering the site from a Web browser window you should be seen only “Hello World”
Do … while loop
Interrupting performances loop