Php versions – ClamAV scanning with PHP 8 – Not a regular file

I’m migrating everything I have from Ubuntu 20.04 to 23.04. The one and only thing, in a long list, I’m struggling with is a web form that uses ClamAV to scan uploaded files. On the old server it works fine. On the new server I persistenly get:
fd[10]: Not a regular file. ERROR
(that’s from /var/log/clamav/clamav.log) and it returns code 2 to the exec command and the following output from $out

(
    [0] => /tmp/php0HjwDM: Not a regular file ERROR
    [1] => 
    [2] => ----------- SCAN SUMMARY -----------
    [3] => Infected files: 0
    [4] => Total errors: 1
    [5] => Time: 0.000 sec (0 m 0 s)
    [6] => Start Date: 2023:06:28 17:08:03
    [7] => End Date:   2023:06:28 17:08:03
)

And after moving the file I then scan it again (for testing)

Array
(
    [0] => /import/myfile.csv: Not a regular file ERROR
    [1] => 
    [2] => ----------- SCAN SUMMARY -----------
    [3] => Infected files: 0
    [4] => Total errors: 1
    [5] => Time: 0.000 sec (0 m 0 s)
    [6] => Start Date: 2023:06:28 17:08:03
    [7] => End Date:   2023:06:28 17:08:03
)

Here’s the test code:

if ($_POST) {
$uploadfile = '/import/' . basename($_FILES['userfile']['name']);
$scanpath=escapeshellarg($_FILES['userfile']['tmp_name']);
$cmd='clamdscan --fdpass '.$scanpath;
$retcode=-1;
$out='';
exec($cmd,$out,$retcode);
echo $retcode.'<br /><pre>';
print_r ($out);
echo '</pre>';
echo '<br />Now moving <br />';
move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile);
$cmd='clamdscan --fdpass '.$uploadfile;
$retcode=-1;
$out='';
exec($cmd,$out,$retcode);
echo $retcode.'<br /><pre>';
print_r ($out);
echo '</pre>';
}
?>

<form enctype="multipart/form-data" action="testpost.php" method="POST">
    Send this file: <input name="userfile" type="file" />
    <input type="submit" value="Send File" />
</form>

Tried with various file types, tried configure clamav to run as www-data (after sorting socket folder permissions). Tried with different files. The "move" and second scan, in the above, was to prove there weren’t issues with the temporary /tmp/ version of the uploaded file.
/import/ has 777 permissions just for testing
Running clamdscan –fdpass myfile.csv from a shell from within the /import folder works just fine, as well as doing it with sudo -u www-data or sudo -u clamav. It just won’t run as expected from PHP’s exec. It certainly tries. Searched in vain for solutions. While other people seem to have had similar issues, they’re not the same as far as I can tell.
Any advice would be greatly appreciated.
Edit 29/06/2023
Using clamscan instead of clamdscan works, except it’s very (unworkably) slow:

Array
(
    [0] => /tmp/phpFahZwQ: OK
    [1] => 
    [2] => ----------- SCAN SUMMARY -----------
    [3] => Known viruses: 8669716
    [4] => Engine version: 0.103.8
    [5] => Scanned directories: 0
    [6] => Scanned files: 1
    [7] => Infected files: 0
    [8] => Data scanned: 0.00 MB
    [9] => Data read: 0.00 MB (ratio 0.00:1)
    [10] => Time: 13.043 sec (0 m 13 s)
    [11] => Start Date: 2023:06:29 11:39:06
    [12] => End Date:   2023:06:29 11:39:19
)