The include_once statement includes and evaluates the specified file during the execution of the script. This is a behavior similar to the include statement, with the only difference being that if the code from a file has already been included, it will not be included again.
| Syntax | Description |
|---|---|
| include_once filename; | includes the specified file into current script filename can be referenced by a variable filename is case-sensitive |
| test.php |
|---|
<?php
echo "Hello\r\n";
?>| init.php |
|---|
<?php
include "test.php"; // include test.php
include "test.php"; // include test.php again
include_once "test.php"; // not include test.php
?>[result]
Hello
Hello