PHP concatenate variable with constant

Question

I have a static View class that gets passed a string from another class. When the string is passed through as a variable it works. When I change it to a constant the error is:

[17-Feb-2016 19:08:48 Europe/Berlin] PHP Warning: include(): Failed opening '/Applications/MAMP/htdocs/its_vegan/scripts/back_end/views/template' for inclusion (include_path='.:/Applications/MAMP/bin/php/php7.0.0/lib/php') in /Applications/MAMP/htdocs/its_vegan/scripts/back_end/views/view.php on line 23

class View {

    /**
     * -------------------------------------
     * Render a Template.
     * -------------------------------------
     * 
     * @param $filePath - include path to the template.
     * @param null $viewData - any data to be used within the template.
     * @return string - 
     * 
     */
    public static function render( $filePath, $viewData = null ) {

        // Was any data sent through?
        ( $viewData ) ? extract( $viewData ) : null;

        ob_start();
        include ( $filePath );// error on this line
        $template = ob_get_contents();
        ob_end_clean();

        return $template;
    }
}

class CountrySelect {

    const template = 'select_template.php'; //the const is template

    public static function display() {

        if ( class_exists( 'View' ) ) {

            // Get the full path to the template file.

            $templatePath = dirname( __FILE__ ) . '/' . template; //the const is template

            $viewData = array(
                "options" => '_countries',
                "optionsText" => 'name',
                "optionsValue" => 'geonameId',
                "value" => 'selectedCountry',
                "caption" => 'Country'
            );

            // Return the rendered HTML
            return View::render( $templatePath, $viewData );

        }
        else {
            return "You are trying to render a template, but we can't find the View Class";
        }
    }
}

What did work was having this in the CountrySelect:

$templatePath = dirname( __FILE__ ) . '/' . static::$template;

Why does the template have to be static? Can I make it a static constant?

Answer 1

You could also use self::template
Since class constants are defined at a per class level instead of per-object, static::template will refer to the same, unless you have a child class. (See https://secure.php.net/manual/en/language.oop5.late-static-bindings.php )

template refers to a global constant (eg by define('template', 'value'); )

Answer 2

At this line

$templatePath = dirname( __FILE__ ) . '/' . template; 

template is not constant, because constant template declared inside class. This code works similar

$templatePath = dirname( __FILE__ ) . '/template'; 

so, use static::template