PHP ...Lesson Three

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Variables in PHP
Variables in PHP are represented by a dollar sign followed by the name of the variable. The variable name is case-sensitive, so $myvar is different from $myVar.

A valid variable name starts with a letter or underscore, followed by any number of letters, numbers, or underscores.
Example :




PHP Superglobals
Superglobals are variables that available anywhere in the program code. They are :
$_SERVERVariables set by the web server or otherwise directly related to the execution environment of the current script. One useful variable is $_SERVER['REMOTE_ADDR'] which you can use to know you website visitor's IP address


Variable Scope
The scope of a variable is the context within which it is defined. Basically you can not access a variable which is defined in different scope.
The script below will not produce any output because the function Test() declares no $a variable. The echo statement looks for a local version of the $a variable, and it has not been assigned a value within this scope. Depending on error_reporting value in php.ini the script below will print nothing or issue an error message.



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