Help refactoring PHP function

I have the following PHP function from an ExpressionEngine plugin and having a little difficulty figuring out how to refactor this to be more efficient, and shorter.

    public function checkuser() {
        $first_name = $this->EE->input->post("FirstName");
        $last_name  = $this->EE->input->post("LastName");
        $DOB        = $this->EE->input->post("DOB");
        $email      = $this->EE->input->post("Email");
        $this->return_data['error'] = '';
        
        $senddata = array("SearchBy"       =>  "FIND",
                          "UserID"         =>  null,
                          "Username"       =>  null,
                          "Sha1Password"   =>  null,
                          "FirstName"      =>  $first_name,
                          "LastName"       =>  $last_name,
                          "DOB"            =>  $DOB,
                          "Address"        =>  null,
                          "Zip"            =>  null,
                          "Phone"          =>  null,
                          "Email"          =>  $email 
        );

        $url = $this->scic_db_url.'SC2/FindUser';
        $ch = curl_init();

        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_MAXREDIRS, 3);
        curl_setopt($ch, CURLOPT_USERAGENT, 'HAC');
        curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
        curl_setopt($ch, CURLOPT_TIMEOUT, 120);
        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($senddata));
        $re = curl_exec($ch);
        $curl_err = curl_error($ch);
        curl_close($ch);
        $part = json_decode($re, true);

        if($curl_err) return $curl_err;
        if(!array_key_exists("Exception", $part)) {
            // User exists. check email for the $part to see if it matches one passed?
            if($part["Primary_Email_Address"] !== $email) {
                $this->return_data['error'] = "* Your account information is in our database, however, it contains a different email address.";
            } else {
                $this->return_data['error'] = "* An Account with this email has already been created";
            }
        } elseif(strpos($part["Message"],"No records found") > -1) {
            // Person with that information doesn't exist but let's check for the email addy once again, for safeties sake
            $senddata = array("SearchBy"       =>  "EMAIL",
                              "UserID"         =>  null,
                              "Username"       =>  null,
                              "Sha1Password"   =>  null,
                              "FirstName"      =>  null,
                              "LastName"       =>  null,
                              "DOB"            =>  null,
                              "Address"        =>  null,
                              "Zip"            =>  null,
                              "Phone"          =>  null,
                              "Email"          =>  $email // ONLY REQUIRED parameter for EMAIL searches
            );

            $url = $this->scic_db_url.'SC2/FindUser';
            $ch = curl_init();

            curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
            curl_setopt($ch, CURLOPT_MAXREDIRS, 3);
            curl_setopt($ch, CURLOPT_USERAGENT, 'HAC');
            curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, 30);
            curl_setopt($ch, CURLOPT_TIMEOUT, 120);
            curl_setopt($ch, CURLOPT_URL, $url);
            curl_setopt($ch, CURLOPT_POST, true);
            curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($senddata));
            $re = curl_exec($ch);
            $curl_err = curl_error($ch);
            curl_close($ch);
            $part = json_decode($re, true);
            if($part["Primary_Email_Address"] === $email) {
                $this->return_data['error'] = "* An Account with this email has already been created";
            }
        } else {
            $this->return_data['success'] = true;
        }
        return json_encode($this->return_data);
    }

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I'd preferably like to have a function that I could pass the method, "FIND" or "EMAIL" and the arguments and have it return either the error message or success.