Common php database configuration files

Config. php file:
Copy codeThe Code is as follows:
<? Php
$ Db_name = "test ";
$ Db_username = "root ";
Global $ db_password;
?>

Database Operation class (call configuration file) db. fun. php:
Copy codeThe Code is as follows:
<? Php
Require ("config/config. php ");
Class db {
Function fun (){
Global $ db_username, $ db_password;
Echo "database username:". $ db_username. "<br/> ";
Echo "Database Password:". $ db_password. "<br/> ";
}
}
?>

Application file test. php:
Copy codeThe Code is as follows:
<? Php
Require ("include/db. fun. php ");
$ A = new db ();
$ A-> fun ();
?>

Global keyword:
Copy codeThe Code is as follows:
<? Php
$ A = 1;/* global scope */
Function Test ()
{
Echo $ a;/* reference to local scope variable */
}
Test ();
?>

This script does not have any output, because the echo statement references a local version of variable $ a and is not assigned a value within this range. You may notice that the global variables in PHP are a little different from those in C language. In C language, global variables automatically take effect in functions unless they are overwritten by local variables. This may cause some problems. Some may carelessly change a global variable. Global variables in PHP must be declared as global when used in functions.
Copy codeThe Code is as follows:
<? Php
$ A = 1;
$ B = 2;
Function Sum ()
{
Global $ a, $ B;
$ B = $ a + $ B;
}
Sum ();
Echo $ B;
?>

The output of the above script is "3 ". Specify the global variables $ a and $ B in the function. All referenced variables of any variable point to the global variable. PHP has no limit on the maximum number of global variables that a function can declare.