如何在php $ div中关闭double include_once

I am including two files in my index page:

$PageData = new Page_Data(); 
$PageData->title ="Welcome to my page";
$div=  "<div class='login-form'>" . include_once "views/navigation.php" . include_once "controllers/login.php" . "</div>";
$PageData->content .=$div;

And I get these two errors.

Warning: include_once(controllers/login.php): failed to open stream: No such file or directory in C:\Users\kalle_000\Documents\KEA\3rd Semester\3rd Module\Module_8\PHP_new\index.php on line 9

Warning: include_once(): Failed opening 'controllers/login.php' for inclusion (include_path='.;C:\php\pear') in C:\Users\kalle_000\Documents\KEA\3rd Semester\3rd Module\Module_8\PHP_new\index.php on line 9 test content

What am I doing wrong? All the files are in the right folder where they should be. Any help appreciated!

I changed the syntax to this:

$PageData = new Page_Data(); 
$PageData->title ="Welcome to my page";
$div=  "<div class='login-form'>";
$div.= include_once ("views/navigation.php");
$div.= include_once ("controllers/login.php");
$div.= "</div>";


$PageData->content .=$div;

For some reason, the browser didn't understand the previous syntax, but gets this and now it works perfectly. Thanks for the help.

include_once "views/navigation.php" . include_once "controllers/login.php" . "</div>"

This is basically evaluated as

include_once ("views/navigation.php" . (include_once ("controllers/login.php" . "</div>")))

That means first "controllers/login.php" . "</div>" is tried to be included, then views/navigation.php0 ("views/navigation.php" + result of the first include). That obviously won't work very well.

Further, the included content probably won't be concatenated into $div either, but output directly.
You probably want:

ob_start();
echo "<div class='login-form'>";
include_once "views/navigation.php";
include_once "controllers/login.php";
echo "</div>";
$div = ob_get_clean();