Write the database username, password, and other information to the configuration file config. in php, include or require in the file that needs to reference the configuration file content, and use the global keyword in the function to compile the variables such as the database name and password, in this way, the config. php file:
Copy codeThe code is as follows:
$ Db_name = "test ";
$ Db_username = "root ";
Global $ db_password;
?>
Database operation class (call configuration file) db. fun. php:
Copy codeThe code is as follows:
Require ("config/config. php ");
Class db {
Function fun (){
Global $ db_username, $ db_password;
Echo "database username:". $ db_username ."
";
Echo "database password:". $ db_password ."
";
}
}
?>
Application File test. php:
Copy codeThe code is as follows:
Require ("include/db. fun. php ");
$ A = new db ();
$ A-> fun ();
?>
Global keyword:
Copy codeThe code is as follows:
$ 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:
$ 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.
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