How to use $this outside a class object?

Question

I am somewhat experienced with PHP but not so much with Joomla's design. I have an event management component (iCagenda). It has a page to edit events. There is the ability to add custom fields. But it doesn't allow a date type field. So I am trying to copy how the component uses an existing date field (startdate).

In the file that handles the event input, there is this, for instance:

<?php echo $this->form->getInput('startdate'); ?>

At the very top of the page there is this

defined('_JEXEC') or die();
JHtml::_('behavior.tooltip');
JHtml::_('behavior.formvalidation');
$app = JFactory::getApplication();
$document = JFactory::getDocument();

then later, this

JHtml::_('formbehavior.chosen', 'select');
jimport('joomla.html.html.bootstrap');

This page does not have a top level function or anything, it just goes right into if-else statements. Not being familiar with object-oriented terminology, I have no idea if this is considered an object or what.

This page calls a function to display custom fields:

echo icagendaCustomfields::loader(2);

Then in the file that handles the display of custom fields, there is this at the top

defined('_JEXEC') or die();
class icagendaCustomfields
{

In the loader function there is this

static public function loader($parent_form)
{
    $app = JFactory::getApplication();
    $session = JFactory::getSession();

And eventually a call to icagendaCustomfields::displayField

In displayField, there is this call

$app = JFactory::getApplication();

Then the function creates the form html, which is where I am trying to change the code to make one of he custom text fields a date field. Here is the relevant code:

$cf_fields.= '<div class="' . $ic_prefix . 'controls' . $is_list . '">';

    // Field Type TEXT
    if ($type == 'text')
    {

        // enable a date field here (for instance for the registation due date custom field)
        if ($slug === "registration_due_date"){

        // First - try and test that I can get the already existing event startdate field to display

        $cf_fields.= $this->form->getInput('startdate');
        } else {

        $cf_fields.= '<input type="'.$type.'"';
        $cf_fields.= ' id="' . $slug . '_slug"';
        $cf_fields.= ' name="' . $ic_data . '['.$slug.']"';
        $cf_fields.= ' value="'.$value.'"';
        $cf_fields.= ' placeholder="'.$options.'"';
        if ($app->isAdmin()) $cf_fields.= $text_required;
//      if ($app->isSite()) $cf_fields.= $text_required;
        $cf_fields.= ' />';
        }
    }

This fails above at this line: $cf_fields.= $this->form->getInput('startdate');

The error is "Using $this when not in object context"

Now, this startdate form is an already existing field in the event edit section, so I am just adding this line to confirm I can get things working before going on. Ultimately I need the registration_due_date field to act like the startdate field (i.e. a calendar date select box).

Any ideas? Sorry for such a long post. I am just trying to understand where in the flow to best make changes.

Answer 1

$this can only be called inside an instantiated PHP class, an object.

If you are calling an static method from PHP class, then there is no object context. Thus, $this will fail.

To call "loader" method, you have to write:

$agenda = new icagendaCustomfields; // Add params if they are required
$agenda->loader();