PHP Database configuration file Implementation Method Example

$db _name= "Test"; $db _username= "root"; Global $db _password; ?> Copy Code 2, Database operation class (call config file) db.fun.php: Require ("config/config.php"); Class db{ function Fun () { Global $db _username, $db _password; echo "Database user name:" $db _username. " "; echo "Database password:". $db _password. " "; } } ?> Copy Code 3, application file test.php: Require ("include/db.fun.php"); $a = new db (); $a->fun (); ?> Copy Code 4,global Keywords: $a = 1; /* Global scope */ function Test () { echo $a; /* Reference to local scope variable */ } Test (); ?> Copy Code This script does not have any output, because the Echo statement refers to a local version of the variable $a, and within that range, it is not assigned a value. PHP has a slightly different global variable from the C language, and in C, global variables are automatically applied in functions unless overridden by local variables. This can cause some problems, and some people may change a global variable. A global variable in PHP must be declared global when used in a function. $a = 1; $b = 2; function Sum () { Global $a, $b; $b = $a + $b; } Sum (); Echo $b; ?> Copy Code The output of the above script will be "3". The global variable $a and $b are declared in the function, and all reference variables of any variable are pointed to the global variable. PHP has no restrictions on the maximum number of global variables a function can declare.

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