HTML/PHP form suddenly stopped working without changing code

I have a website which displays a directory/folders where I can upload multiple files onto said directory/folder to easily access important documents/articles. It’s been working beautifully for about a year and suddenly stopped working the last month. I know that I have not changed my code accidentally because I have several folders with the same php file copy/pasted into each folder and would be impossible for me to have changed each php file.

What’s weird is that if I try uploading 1 file at a time, it fails and uploads a 0 byte document. If I upload multiple files, the first file fails & uploads a 0 byte document, but all subsequent files are able to upload successfully.

I don’t know if something changed with my hosting provider or something changed with input type=file usage but would love help. Thanks!!

screenshot of website format. first file attempted to upload listed as 0 bytes, second file able to upload

HTML

<form action="upload.php" method="post" enctype="multipart/form-data">
    <input type="file" name="fileToUpload[]" id="fileToUpload" multiple="multiple">
    <input type="submit" value="Upload" name="submit">
</form>

PHP

<?php
$targetDir = __DIR__ . '/'; // Directory where uploaded files will be stored

if(isset($_POST["submit"])) {
// Loop through each uploaded file
for ($i = 0; $i < count($_FILES["fileToUpload"]["name"]); $i++) {
    $targetFile = $targetDir . basename($_FILES["fileToUpload"]["name"][$i]); // Get the filename of the uploaded file

    // Check if file already exists
    if (file_exists($targetFile)) {
        echo '<script>alert("Sorry, the file '. basename($_FILES["fileToUpload"]["name"][$i]). ' already exists.");</script>';
        continue; // Skip to the next iteration of the loop
    }

    // Check file size (optional)
    if ($_FILES["fileToUpload"]["size"][$i] > 100000000) { // Adjust the file size limit as per your requirements
         echo '<script>alert("Sorry, your file '. basename($_FILES["fileToUpload"]["name"][$i]). ' is too large.");</script>';
        continue; // Skip to the next iteration of the loop
    }

    // If the upload is successful, move the uploaded file to the target directory
    if (move_uploaded_file($_FILES["fileToUpload"]["tmp_name"][$i], $targetFile)) {
        echo '<script>alert("The file '. basename($_FILES["fileToUpload"]["name"][$i]). ' has been uploaded.");</script>';
    } else {
        echo '<script>alert("Sorry, there was an error uploading your file.");</script>';
    }
}

// Redirect back to the upload page
$redirectUrl = rtrim(dirname($_SERVER['PHP_SELF']), '/') . '/list.php';
echo '<script>window.location.href = "'.$redirectUrl.'";</script>';
}
?>

I have tried several different computers (personal and public ones) on chrome, safari, phone brave app, and nothing works, so suspect it is code-related or server related.

I tried changing permissions (currently 0755), but no luck there.

I don’t really know much about changing specifics of files/settings on hosting server… I did try to disable htaccess and re-enable, but that didn’t do anything.