Using add_filters() , apply_filter(), add_action() and do_action() in extending a plugin

Question

Suppose i am developing a plugin that is related too booking.Next time i want to add an add-ons on that plugin for payment.Then i added another add-ons for paypal payment.

Assume that below is the payment gateway UI interface in html

<div class="payments-options">
    <div class="bank-payment"></div>
    <div class="cash-on-delivery"></div>
    <!--- Here i want to add a new div for paypal same as other two ---->
</div>

So how can i use add_filters() , apply_filter(), add_action() and do_action() Here to achieve this?

Answer 1

It's a very broad question, but my approach would look something like this:

I'd replace your code with this:

<?php my_the_payment_options(); ?>

And then in my plugin:

function my_the_payment_options() {
    $payment_options = get_my_available_payment_options();
    if ( $payment_options ) :
    ?>
    <div class="payments-options">
        <?php foreach ( $payment_options as $k => $v ) call_user_func( $v['callback'] ); ?>
    </div>
    <?php
    endif;
}

function get_my_available_payment_options() {
    return apply_filters( 'get_my_available_payment_options', array() );
}

and then in code adding payment method (here for PayPal):

function my_add_paypal( $available_payments ) {
    $available_payments[ 'paypal' ] => array(
        'callback' => 'my_paypal_callback',
        // some other params if needed
    );
}
add_filter( 'get_my_available_payment_options', 'my_add_paypal' );

function my_paypal_callback() {
    ?>
    <div class="paypal-div"></div>
    <?php
}

Disclaimer: Treat this code as way to show the idea and not as working solution :)