public function attr($keys = [])
    {
        if (!is_array($keys)) {
            $keys = [$keys];
        }
        
        $out = '';
        foreach ($keys as $key) {
            $value = $this->getValue($key)->attr();
            if (!empty($value)) {
                $out .= ' ' . $value;
            }
        }
        return ltrim($out, ' ');
    }
public function attr($keys = [])
    {
        if (!is_array($keys)) {
            $keys = [$keys];
        }
        
        $out = '';
        foreach ($keys as $key) {
            $value = $this->getValue($key)->attr();
            if (!empty($value)) {
                $out .= ' ' . $value;
            }
        }
        return ltrim($out, ' ');
    }
public function attr ( $ keys = [ ] ) { if ( ! is_array ( $ keys ) ) { $ keys = [ $ keys ] ; } $ out = '' ; foreach ( $ keys as $ key ) { $ value = $ this -> getValue ( $ key ) -> attr ( ) ; if ( ! empty ( $ value ) ) { $ out .= ' ' . $ value ; } } return ltrim ( $ out , ' ' ) ; }
Renders the all the given keys as HTML element attributes.

@param array|string $keys
@return string
Renders the all the given keys as HTML element attributes .