What is the Diffrent?? "includes-require"

[fireblade]

WHat is the different amOng....

1. includes ("db.php");
2. require("db.php");
3. require_once("db.php");

can anyOne give me the expLainatiOn???

[NogDog]

include
include_once
require
require_once
If there's something specific in the manual you don't understand, let us know.

[fireblade]

thanx

[n_alexiev]

require_once checks that if is included file .
If its included before doesnt include it again.
require_once takes more system memory

[sanchez_1960]

require_once checks that if is included file .
If its included before doesnt include it again.
require_once takes more system memory

I'm always using require_once heh.