suggested fix

I believe the problem is that certain hosts don’t include the finfo function by default, even in PHP5.3… I was able to get around this by changing the function near line 136 to:

function _mime_content_type($filename) {
	if (function_exists("finfo_file")) {
		$finfo = finfo_open(FILEINFO_MIME_TYPE); // return mime type ala mimetype extension
		$mime = finfo_file($finfo, $absoluteFilePath);
		finfo_close($finfo);
		return $mime;
	} else if (function_exists("mime_content_type")) {
		return mime_content_type($absoluteFilePath);
	} else if (!stristr(ini_get("disable_functions"), "shell_exec")) {
	// http://stackoverflow.com/a/134930/1593459
	$file = escapeshellarg($absoluteFilePath);
	$mime = shell_exec("file -bi " . $absoluteFilePath);
	return $mime;
} else {
	return false;
}

/*
	// Instantiate finfo
	$result = new finfo_open();
	// Get Mime Type with PHP 5.3 compatible method
	if (is_resource($result) === true) {
		return $result->file($filename, FILEINFO_MIME_TYPE);
	}

	return false;
*/
}

http://wordpress.org/plugins/image-teleporter/