lib/mail/OpenTracking.php
public function jsonSerialize()
    {
        return array_filter(
            [
                'enable' => $this->getEnable(),
                'substitution_tag' => $this->getSubstitutionTag()
            ],
            function ($value) {
                return $value !== null;
            }
        ) ?: null;
    }
public function jsonSerialize()
    {
        return array_filter(
            [
                'enable' => $this->getEnable(),
                'substitution_tag' => $this->getSubstitutionTag()
            ],
            function ($value) {
                return $value !== null;
            }
        ) ?: null;
    }
public function jsonSerialize ( ) { return array_filter ( [ 'enable' => $ this -> getEnable ( ) , 'substitution_tag' => $ this -> getSubstitutionTag ( ) ] , function ( $ value ) { return $ value !== null ; } ) ? : null ; }
Return an array representing a OpenTracking object for the Twilio SendGrid API

@return null|array
Return an array representing a OpenTracking object for the Twilio SendGrid API