File upload validation in PHP

Question

I'm using the following php code to upload a csv file. I want to use a good validation and not only via mime type or file extension. How can I do that?

if (isset($_POST['submit'])) {
    $isfileok = false;
    if (is_uploaded_file($_FILES['filename']['tmp_name'])) {
        echo "<h1>" . "File ". $_FILES['filename']['name'] ." uploaded successfully." . "</h1>";
    $isfileok = true;
    }
    if($isfileok){
        //do something
    }
}

Answer 1

You can look for patterns within the file content to determine the type. We solved this exact problem in a project I worked on using mime magic detection functionality in Tika. https://tika.apache.org/1.1/detection.html