Php database configuration file implementation example

Php database configuration file implementation 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. application 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 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. 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 change a global variable. Global variables in PHP must be declared as 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 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.