Busting The Loop Lies

“The Loop” lies to us all, don’t let it trick you. An intervention with the loop is past due. Lets walk through mastering its evil ways together. What is the best way to loop? Should you use get_posts, WP_Query or query_posts? Why does pagination break? How do you loop at all and what is the loop? How can you optimize the loop and decrease load time? Get the most out of the loop! In this talk we will master the backbone of WordPress. Together and answer these important and overlooked questions in turn.

Schedule:
http://2013.birmingham.wordcamp.org/session/busting-the-loop-lies/

Links:
http://wordpress.tv/2013/03/15/andrew-nacin-wp_query-wordpress-in-depth/
http://wordpress.stackexchange.com/questions/1753/when-should-you-use-wp-query-vs-query-posts-vs-get-posts
http://codex.wordpress.org/Function_Reference/WP_Query
http://codex.wordpress.org/Plugin_API/Action_Reference/pre_get_posts

Transcript

1. Busting
   The Loop Lies
   Kevin Dees
   Robojuice
   Sunday, August 25, 13
   

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2. #looplies
   Sunday, August 25, 13
   

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3. Why do you
   need to know
   “The Loop” Lies?
   Sunday, August 25, 13
   

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4. The very basics....
   What is “The Loop”
   Sunday, August 25, 13
   

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5. 
   
   
   
   
   
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6. The very basics....
   Where “The Loop”
   comes from
   Sunday, August 25, 13
   

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7. “The Loop”Lives
   in Your
   Template Files
   Sunday, August 25, 13
   

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8. index.php
   archive.php
   404.php
   home.php
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9. What are
   “The Loop” Lies?
   Sunday, August 25, 13
   

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10. “The Loop” is hard!
    LIE
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11. 
    
    
    
    
    
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12. The Main Loop
    vs
    Everything else
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13. $wp_query
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14. $wp_the_query
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15. NEVER USE IT
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16. A puppy dies
    every time you use it
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17. The Main Loop
    // wp-settings.php around line 220
    $wp_the_query = new WP_Query();
    $wp_query = $wp_the_query;
    Sunday, August 25, 13
    

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18. Everything else
    // includes folder post.php around line 1627
    function get_posts($args = null) {
    // lots of code
    $get_posts = new WP_Query;
    return $get_posts->query($r);
    }
    Sunday, August 25, 13
    

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19. 4 common ways to
    use “The Loop”
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20. 4 common lies
    about them
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21. query_posts is great
    LIE
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22. It is used to edit the
    main loop
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23. query_posts( array( 'posts_per_page' => 5 );
    while ( have_posts() ) : the_post();
    echo '';
    the_title();
    echo '';
    endwhile;
    wp_reset_query();
    ?>
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24. NEVER USE IT
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25. You run the main
    query twice
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26. You break
    pagination
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27. A puppy dies
    every time you use it
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28. get_posts uses
    foreach so don’t
    touch it
    LIE
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29. $theposts = get_posts( $args );
    foreach($theposts as $post) :
    setup_postdata($post);
    ?>
    
    
    
    endforeach;
    wp_reset_postdata();
    ?>
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30. WP_Query is too
    verbose to use
    LIE
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31. function get_last_five() {
    $last_five = new WP_Query( array(
    'post_type' => 'any',
    'posts_per_page' => 5 ));
    if ( $last_five->have_posts() ) {
    while ( $last_five->have_posts() ) {
    $last_five->the_post();
    $title = get_the_title();
    echo "{$title}";
    }
    }
    wp_reset_postdata();
    }
    Sunday, August 25, 13
    

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32. pre_get_posts is
    confusing
    LIE
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33. add_action( 'pre_get_posts', 'demo_main_loop' );
    function demo_main_loop($query) {
    if ( $query->is_main_query() && !is_admin() ) :
    // do stuff
    endif;
    return;
    }
    ?>
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34. // do stuff
    if ( is_home() ) {
    $query->set('post_type', 'any');
    $query->set('posts_per_page', 3);
    }
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35. “The Loop” lacks
    powerful selection
    LIE
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36. Sunday, August 25, 13
    

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37. // do stuff
    $meta_args = array( array(
    'key' => 'demo_on_home_page',
    'value' => 1 ) );
    if ( is_home() ) {
    $query->set('post_type', 'any');
    $query->set('meta_query', $meta_args);
    $query->set('posts_per_page', 3);
    }
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38. “The Loop” only runs
    1 query
    LIE
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39. 4 queries
    are run
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40. 1 : the posts
    2 : number of posts
    3 : meta data
    4 : taxonomy data
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41. $numq = 0;
    add_filter('query', 'numQ');
    function numQ($q) {
    global $numq;
    $numq++;
    return $q;
    }
    echo $numq;
    ?>
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42. Can you have just
    1 query?
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43. global $numq;
    $last_five = new WP_Query( array(
    'post_type' => 'any',
    'posts_per_page' => 2,
    'no_found_rows' => true, // rows
    'update_post_meta_cache' => false, // meta
    'update_post_term_cache' => false // tax
    ));
    // the loop
    echo “Total Queries: {$numq}”;
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44. if ( $last_five->have_posts() ) {
    echo "Last Posted Items";
    while ( $last_five->have_posts() ) {
    $last_five->the_post();
    $title = get_the_title();
    $link = get_permalink();
    echo "{$title}";
    }
    echo "";
    }
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45. Thank You
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