Variable generation and scope in PHP_PHP tutorial

In PHP, you do not need to notify PHP before using a variable. The place where a variable is used for the first time determines the scope of the variable. In some programming languages ​​such as C, global variables are visible inside the function. This is not the case in PHP. When creating a function in PHP, you must explicitly declare the global variables to be used using glob.
For example:

function printcity($cityname)
{
print("Your favorite city is: $cityname");
}
$city ="Beijing";
function citya() //Define a function
{
$city="Guangzhou";
printcity($city);
}
function cityb( )
{
$city="Shenzhen";
printcity($city);
}
function cityc()
{
global $city; // Get a reputation Global variable
printcity($city);
}
citya();//Output Guangzhou
cityb();//Output Shenzhen
cityc();//Output Beijing
?>
Note:
The variables inside the function are only valid when the function is used. Once the function ends, all variables of the function will be cleared.