PHP variable generation and scope

In PHP, you do not have to notify PHP beforehand before using a variable. The first time variables are used, the scope of variables is determined. Some programming languages such as the C language global variables are visible inside the function. This is not the case in PHP. When creating a function in PHP, you must use gloabl to declare the global variables to be used.
For example:
Function printcity ($ cityname)
{
Print ("your favorite city is: $ cityname ");
}
$ City = "Beijing ";
Function citya () // defines a function
{
$ City = "Guangzhou ";
Printcity ($ city );
}
Function cityb ()
{
$ City = "Shenzhen ";
Printcity ($ city );
}
Function cityc ()
{
Global $ city; // a global variable
Printcity ($ city );
}
Citya (); // output to Guangzhou
Cityb (); // output to Shenzhen
Cityc (); // output to Beijing
?>
Note:
The internal variables of the function are valid only when the function is used. Once the function ends, all the variables of the function are cleared.