Certificate File Upload Issue

Hello All,

I am working for a while on YII2 and its wonderful.

I am facing an issue regarding the file upload. I want to upload certificate file with .pem extension.

This is failing, when I change the rule to txt it works fine but not with pem file.

here are the rules in which I even tried to user checkExtensionByMimeType but no luck.

with checkExtensionByMimeType its giving extension error and with this setting on giving the mimeType error

public function rules()


        return [

            [['file'], 'required', 'message' => 'Please select a file.'],

            [['file'], 'file', 'extensions' => 'pem, cer, crt', 'checkExtensionByMimeType' => true, 'mimeTypes' => 'application/x-x509-ca-cert'],