PHP database configuration file implementation method example

$db_name="test";
$db_username="root";
global $db_password;
?>

2, database operation class (call configuration File) db.fun.php:

require("config/config.php");
class db{
function fun(){
global $db_username,$db_password;
echo "Database username: ".$ db_username."";
echo "Database password:".$db_password."";
}
}
?>

3, apply File test.php:

require("include/db.fun.php");
$a= new db();
$a->fun();
?>

4, global keyword:

$a = 1; /* global scope */
function Test()
{
echo $a; /* reference to local scope variable */
}
Test();
?>

This script will not produce any output because the echo statement refers to a local version of the variable $a, and it is not assigned a value in this scope. PHP's global variables are a little different from C language. In C language, global variables automatically take effect in functions unless overridden by local variables. This may cause some problems, someone may change a global variable. Global variables in PHP must be declared global when used in functions.

$a = 1;
$b = 2;
function Sum()
{
global $a, $b;
$b = $a + $b;
}
 Sum();
echo $b;
?>

The output of the above script will be "3". Global variables $a and $b are declared in the function, and all reference variables of any variable will point to the global variables. PHP has no limit on the maximum number of global variables that a function can declare.