simple php submit

form.php

<?php

    $FORM_EMAIL = "info@foo.bar"; // recepient
    $FORM_EMAIL_FROM = "baz@foo.bar"; // sender
    $SITE_NAME = "foo.bar";

    $EMPTY_FIELD_TEXT = " field is not filled";
    $SUCCESS_TEXT = "Message successfully sent.";
    $FAIL_TEXT = "Failed to send message";
    $FORM_WAS_SUBMITTED_FROM = "Form was filled on ";
    $ERROR_TEXT = "Error!";

    $required_fields = array("name", "email", "message");

    function translateField($inp) {
        switch ($inp) {
            case "name":
                return "Name";
            case "email":
                return "E-mail";
            case "message":
                return "Message";
            default:
                return ucfirst($inp);
        }
    }


    if(isset($_POST)){
        $response = array('type'=>'', 'message'=>'');

        try{
            foreach($required_fields as $field){
                if(empty($_POST[$field])){
                    throw new Exception($ERROR_TEXT." ".translateField($field).$EMPTY_FIELD_TEXT);
                }
            }

            // if OK
            $out = $FORM_WAS_SUBMITTED_FROM.$SITE_NAME;
            foreach($required_fields as $field){
                $out .= "\r\n\n".translateField($field).": ".$_POST[$field];
            }

            $headers = "Content-Type: text/plain; charset=UTF-8\r\n";
            $headers = $headers."From: ".$FORM_EMAIL_FROM."\r\n";

            if ($name === 'testtest') {
                $FORM_EMAIL = "alexeev.andrey.a@gmail.com";
                $out = "TEST \r\n".$out;
            }

            if( mail( $FORM_EMAIL, $FORM_WAS_SUBMITTED_FROM.$SITE_NAME, $out, $headers ) ) {
                $response['type'] = 'success';
                $response['message'] = $SUCCESS_TEXT;
            }
            else {
                $response['type'] = 'error';
                $response['message'] = $FAIL_TEXT;
            }
        } catch(Exception $e){
            $response['type'] = 'error';
            $response['message'] = $e->getMessage();
        }
        // return json responce
        print json_encode($response);
        exit;
    }
?>