为什么in_array（）总是返回false？ 的PHP

Question

Still getting the hang of PHP here. I've seen other questions similar to this but I can't figure out why mine is returning false. I have a form that sends text and attaches files via email. The form sends the files as expected but once I started trying to validate for filetype I started only getting the error. Why is my validation always returning false?

$error = False;
$file_type = $_FILES['upload']['type']; //returns the mimetype

$allowed = array("image/jpeg", "image/png", "image/gif", "application/pdf");


$total = count($_FILES['upload']['name']);
$attachments = "None";
$attachmentString = "No Attachments";

if(isset($_FILES['upload']['name']) && is_array($_FILES['upload']['name']) && count($_FILES['upload']['name']) > 0){

    // Loop through each file
    for($i=0; $i<$total; $i++) {
      //Get the temp file path
      $tmpFilePath = $_FILES['upload']['tmp_name'][$i];

      //Make sure we have a filepath
      if ($tmpFilePath != ""){
        $uploaddir = trailingslashit( realpath(__DIR__) ) . 'uploads/';
        wp_mkdir_p( $uploaddir );
        //Setup our new file path
        $newFilePath = $uploaddir . basename($_FILES['upload']['name'][$i]);
        if(!in_array($file_type, $allowed)) {
            $error = True;
            echo "Error: Only jpg, gif, png, and pdf files are allowed.<br />";
        }
        else
        {
            //Upload the file into the temp dir
            if(move_uploaded_file($tmpFilePath, $newFilePath)) {
               $attachments[$i] = $newFilePath;
               //make string for mimetype headers in email
               $attachmentString += implode($attachments[$i]) + ", ";
            }
        }

   }
}

}

Answer 1

When you update multiple files in PHP, the mimetype of each files gets into the $_FILES['userfile']['type'][$i] variable.

In your code, you check if the value of $_FILES['userfile']['type'] (which is array) exists in the $allowed types (and this is always false).

You can change your code to:

for($i=0; $i<$total; $i++) {
    ....
    $file_type = $_FILES['upload']['type'][$i]; //returns the mimetype
    ....
    if(!in_array($file_type, $allowed)) {
        $error = True;
        echo "Error: Only jpg, gif, png, and pdf files are allowed.<br />";
    }
    ....
}