PHP Learning Notes

1. Variable declaration:

$value = "Guest";

$ $value = "Custom";

echo $value. " \ t ". $guest; Guest as the variable name.

2. Variable Scope

(1) Built-in super-global variables, can be accessed anywhere in the code;

(2) constant, once declared, it is global, can be used inside and outside the function;

(3) The function is declared as a global variable, which is the global variable with the same name;

(4) The function is created and declared as a static variable, not accessible outside the function, but the value of this static variable can be preserved;

(5) A variable declared in a function that cannot be accessed outside the function and is invalidated when the function terminates.

PHP Learning Notes