PHP / HTML File Upload Not Recognizing Screenshot Images - php

Question

I am building a file upload tool for my website and am running into a strange issue. The html input is set up to accept image/png, image/jpg, image/jpeg, .pdf files and it works fine when I am using it to upload PDFs or images that came from a camera or a design software.
However, when I upload an image (png) that was a screenshot taken on my Mac, the $_FILES has a value for the name attribute, but has no values for the tmp_name, type, error, size attributes. I've tried renaming the file to see if that was the issue, and that doesn't appear to be the problem either.
This is the output I get when I run print_r($_FILES):
Array ( [fileupload] => Array ( [name] => Array ( [0] => Screen Shot 2020-12-23 at 2.10.06 PM.png ) [type] => Array ( [0] => ) [tmp_name] => Array ( [0] => ) [error] => Array ( [0] => 1 ) [size] => Array ( [0] => 0 ) ) )
Warning: mime_content_type(): Empty filename or path in pro_testupload.php on line 87
Warning: getimagesize(): Filename cannot be empty in pro_testupload.php on line 91
Warning: mime_content_type(): Empty filename or path in pro_testupload.php on line 103
Does anyone have any idea about what is going on here? Below is my code:
HTML Code
<form method="POST" action="_process/pro_testupload.php" enctype="multipart/form-data">
<input type="file" id="fileupload" name="fileupload[]" accept="image/png, image/jpg, image/jpeg, .pdf" multiple required>
<button class="btn waves-effect black waves-light" type="submit">Upload</button>
</form>
PHP Code
// -----------------------------------------------------------------
// FILE FORMAT CHECKING FUNCTIONS
// -----------------------------------------------------------------
function check_image($filename) {
// Check mime type using PHPs own built in functions (as client side mime type is vulnerable to exploitation)
$mime_type = mime_content_type($filename);
$allowed_file_types = ['image/png', 'image/jpeg', 'image/jpg'];
// Check the file is actually an image
$check = getimagesize($filename);
// Perform all checks
if (in_array($mime_type, $allowed_file_types) && is_array($check) !== False) {
return True;
} else {
return False;
}
}
function check_pdf($filename) {
// Check mime type using PHPs own built in functions (as client side mime type is vulnerable to exploitation)
$mime_type = mime_content_type($filename);
$allowed_file_types = ['application/pdf'];
// Perform checks
if (in_array($mime_type, $allowed_file_types)) {
return True;
} else {
return False;
}
}
// -----------------------------------------------------------------
// CHECK FILES TO ENSURE THEY MEET REQUIREMENTS
// -----------------------------------------------------------------
if(!empty(array_filter($_FILES['fileupload']['name']))) {
foreach ($_FILES['fileupload']['tmp_name'] as $key => $value) {
if (!(check_image($_FILES['fileupload']['tmp_name'][$key]) || check_pdf($_FILES['fileupload']['tmp_name'][$key]))) {
echo ("The files do not meet the uploaded file requirements");
exit;
}
}
} else {
echo ("There were no files requested to be uploaded.");
exit;
}