Hooking into WordPress

1. Hooking into WordPress Craig Ralston craig@websolutions.com

2. Why use hooks? • Extend core functionality • Allow others to alter your work craig@websolutions.com

3. What are hooks? Actions Filters MODIFY existing data apply_filters() add_filter() has_filter() remove_filter() DO something new • do_action() • add_action() • has_action() • remove_action() craig@websolutions.com

4. Actions – How are they used? Add an alert to the admin area using a core hook function cor_admin_notice(){?> <divclass="cor_alert"> <h3>Hello World!</h3> </div> <?php} add_action('admin_notices','cor_admin_notice'); Core hook Our function craig@websolutions.com

5. add_action( 'admin_notices', 'cor_admin_notice' ); add_action( $hook, $function, $priority, $args ); $hook – (required) Name of the hook you are attaching to $function – (required) Name of the function you wish to call $priority – (optional) Prioritize multiple functions on the same hook $args – (optional) Number of arguments $function takes craig@websolutions.com

6. Creating Actions function cor_admin_notice(){?> <divclass="cor_alert"> <h3>Hello World!</h3> </div> <?php} craig@websolutions.com

7. Action function cor_admin_notice(){ echo'<div class="cor_alert">'; do_action('before_alert_text'); echo apply_filters('filter_alert_text','<h3>Hello World</h3>'); do_action('after_alert_text'); echo'</div>'; } Filter Action craig@websolutions.com

8. Let’s add in our own stuff now Add our image before the alert message function add_image_above_alert(){ $image_src='/images/alert.png'; echo'<img src="'.$image_src.'" alt="alert image" />'; } add_action('before_alert_text','add_image_above_alert'); Add a paragraph after the alert message function add_text_below_alert(){ echo'<p>Some really awesome text</p>'; } add_action('after_alert_text','add_text_below_alert'); craig@websolutions.com

9. Action function cor_admin_notice(){ echo'<div class="cor_alert">'; do_action('before_alert_text'); echo apply_filters('filter_alert_text','<h3>Hello World</h3>'); do_action('after_alert_text'); echo'</div>'; } Filter Action craig@websolutions.com

10. echo apply_filters('filter_alert_text','<h3>Hello World</h3>'); apply_filters( $hook, $value, $var ); $hook – (required) Name of the filter hook $value – (required) Value to be modified $var – (optional) One or more additional variables passed to the filter functions craig@websolutions.com

11. Let’s change the original alert message function change_alert_text($text){ $text='<h3>Our new custom alert message</h3>'; return$text; } add_filter('filter_alert_text','change_alert_text', 10, 1); craig@websolutions.com

12. functioncor_admin_notice(){ echo'<div class="cor_alert">'; do_action('before_alert_text'); echoapply_filters('filter_alert_text','<h3>Hello World</h3>'); do_action('after_alert_text'); echo'</div>'; } Action Filter Action craig@websolutions.com

13. Filter profanity in the content area function cor_filter_profanity($content){ // Store an array of what we want to consider profanity $profanities=array('badword','alsobad','reallybad'); // Check the content for profanities before output // Replace them with {censored} $content= str_ireplace($profanities,'{censored}',$content); return$content; } add_filter ('the_content','cor_filter_profanity',10,1); craig@websolutions.com

14. Action or Filter? • When Sarah arrives home, tell her to call me. • When Sarah makes her grocery list, make sure she adds beer to the list craig@websolutions.com

15. When Sarah gets home, have her call me. // When Sarah gets home, have her call me. add_action('after_sarah_arrives','sarah_call_craig',10,1); functionsarah_call_craig($sarah_has_phone){ // if $sarah_has_phoneis true if($sarah_has_phone){ echo'Sarah, would you please call Craig? Thanks.'; } } craig@websolutions.com

16. When Sarah makes her grocery list, add beer. // Modify Sarah's grocery list add_filter('sarahs_grocery_list','cor_add_beer', 10, 1 ); functioncor_add_beer($grocery_list){ // Append another item to the list $grocery_list=$grocery_list.' Beer.'; return$grocery_list; } craig@websolutions.com

17. Helpful Resources Questions? http://codex.wordpress.org/Plugin_API http://adambrown.info/p/wp_hooks craig@websolutions.com