10 Useful WordPress functions (and maybe more)

You can't touch the WordPress core, but you can read it! (Slides for my talk at WordPress Meetup Milano)

Transcript

1. wptexturize _wptexturize_pushpop_element wpautop shortcode_unautop seems_utf8
   _wp_specialchars wp_specialchars_decode wp_check_invalid_utf8 utf8_uri_encode
   remove_accents sanitize_file_name sanitize_user sanitize_key sanitize_title
   sanitize_title_for_query sanitize_title_with_dashes sanitize_sql_orderby sanitize_html_class
   convert_chars balanceTags force_balance_tags format_to_edit zeroise backslashit
   trailingslashit untrailingslashit addslashes_gpc stripslashes_deep urlencode_deep
   rawurlencode_deep antispambot _make_url_clickable_cb _make_web_ftp_clickable_cb
   _make_email_clickable_cb make_clickable _split_str_by_whitespace wp_rel_nofollow
   wp_rel_nofollow_callback translate_smiley convert_smilies is_email wp_iso_descrambler
   _wp_iso_convert get_gmt_from_date get_date_from_gmt iso8601_timezone_to_offset
   iso8601_to_datetime popuplinks sanitize_email human_time_diff wp_trim_excerpt
   wp_trim_words ent2ncr wp_richedit_pre wp_htmledit_pre _deep_replace esc_sql esc_url
   esc_url_raw htmlentities2 esc_js esc_html esc_attr esc_textarea tag_escape
   wp_make_link_relative sanitize_option wp_parse_str wp_pre_kses_less_than
   wp_pre_kses_less_than_callback wp_sprintf wp_sprintf_l wp_html_excerpt
   links_add_base_url _links_add_base links_add_target _links_add_target
   normalize_whitespace wp_strip_all_tags sanitize_text_field wp_basename capital_P_dangit
   sanitize_mime_type sanitize_trackback_urls wp_slash wp_unslash get_url_in_content
   10* useful
   WordPress
   functions
   *maybe more
   WordPress Meetup Milano - 5 May 2015
   

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2. Giustino Borzacchiello
   @jubstuff
   

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3. The #1 rule of
   WordPress
   development
   

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5. DON’T TOUCH THE CORE
   

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6. The core
   

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7. The core
   too hot!
   

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8. The core
   

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9. The core
   

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10. /wp-admin
    Functions and templates to bootstrap the
    WordPress admin.
    /wp-includes
    Most WordPress functionality is here.
    

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11. DON’T TOUCH THE CORE
    ... but you can read it!
    

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12. checked()
    Compares the first two arguments and if identical
    marks as checked.
    

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13. wp-includes/general-template.php
    >
    checked()
    

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14. wp-includes/general-template.php
    >
    checked()
    

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15. selected()
    Compares the first two arguments and if identical
    marks as selected.
    wp-includes/general-template.php
    disabled()
    Compares the first two arguments and if identical
    marks as disabled.
    

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16. Escaping functions.
    esc_*
    

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17. ?
    

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18. Escaping functions. < becomes <
    esc_*()
    

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19. ➢ esc_sql
    ➢ esc_url
    ➢ esc_url_raw
    ➢ esc_js
    ➢ esc_html
    ➢ esc_attr
    ➢ esc_textarea
    esc_*()
    wp-includes/formatting.php
    

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20. echo "Hello WordPress Meetup; alert('Ciao!');";
    // Hello WordPress Meetup;
    esc_attr()
    wp-includes/formatting.php
    

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21. echo esc_attr("Hello WordPress Meetup; alert('Ciao’)<br/>");
    // Hello WordPress Meetup;
    // <script>alert('Ciao!');</script>
    esc_attr()
    wp-includes/formatting.php
    

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22. // Retrieving data from user input...
    $name = ( isset( $_POST['name'] ) ) ? $_POST['name'] : '';
    // ...and displaying it
    
    Example: esc_attr()
    wp-includes/formatting.php
    

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23. Test if the current browser runs on a mobile device
    (smart phone, tablet, etc.).
    wp_is_mobile()
    

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24. function add_my_cool_js_effect_on_desktop() {
    if ( wp_is_mobile() ) {
    return;
    }
    wp_enqueue_script('cool-js-effect', PATH_TO_MY_JS);
    }
    wp_is_mobile()
    wp-includes/vars.php
    

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25. Utility functions for filters.
    __return_*()
    

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26. ➢ __return_empty_array
    ➢ __return_null
    ➢ __return_empty_string
    ➢ __return_zero
    ➢ __return_false
    ➢ __return_true
    __return_*()
    wp-includes/functions.php
    

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27. add_filter( 'show_admin_bar', function(){
    return false;
    } );
    Example: __return_false()
    wp-includes/functions.php
    

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28. add_filter( 'show_admin_bar', '__return_false' );
    Example: __return_false()
    wp-includes/functions.php
    

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29. Display a noindex meta tag.
    wp_no_robots()
    

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30. /**
    * Display a noindex meta tag.
    * @since 3.3.0
    */
    function wp_no_robots() {
    echo "\n";
    }
    wp_no_robots()
    wp-includes/general-template.php
    

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31. // Add this to block search engines on page named 'no-search'
    add_action('init', function() {
    if(is_page('no-search')) {
    add_action( 'wp_head', 'wp_no_robots' );
    }
    });
    wp_no_robots()
    wp-includes/general-template.php
    

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32. Merge user defined arguments into defaults array.
    wp_parse_args()
    

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33. $defaults = ['count' => 5, 'orderby' => 'date', 'order' => 'asc',];
    $params = ['orderby' => 'title', 'order' => 'desc',];
    $options = wp_parse_args($params, $defaults);
    // $options = [
    // 'count' => 5,
    // 'orderby' => 'title',
    // 'order' => 'desc',
    // ]
    wp_parse_args()
    wp-includes/functions.php
    

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34. // MyWidget.php
    public function form( $instance ) {
    $defaults = array(
    'num_entries' => 10,
    'widget_title' => __( 'My title', 'ten-func' ),
    'scale' => 10,
    );
    $instance = wp_parse_args( (array) $instance, $defaults );
    // display the form
    }
    wp_parse_args()
    wp-includes/functions.php
    

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35. Extract a slice of an array, given a list of keys.
    wp_array_slice_assoc()
    

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36. $arr = ['one'=> 1, 'two'=> 2, 'three'=> 3, 'four'=> 4, 'five'=> 5 ];
    $odd = wp_array_slice_assoc($arr, ['one', 'three', 'five']);
    ------------------
    array (size=3)
    'one' => int 1
    'three' => int 3
    'five' => int 5
    wp_array_slice_assoc()
    wp-includes/functions.php
    

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37. Send a JSON response back to an Ajax request,
    indicating success.
    wp_send_json_success()
    

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38. jQuery(document).ready(function($) {
    var data = { 'action': 'my_action', 'post_id': 4 };
    jQuery.post(my_ajax_url, data, function(response) {
    alert('This is from PHP: ' + response);
    });
    });
    wp_send_json_success()
    wp-includes/functions.php
    

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39. add_action('wp_ajax_nopriv_my_action', 'my_ajax_handler');
    function my_ajax_handler() {
    $post_id = intval($_POST['post_id']);
    // Retrieve some $output_data related to that post
    wp_send_json_success($output_data);
    }
    wp_send_json_success()
    wp-includes/functions.php
    

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40. jQuery(document).ready(function($) {
    var data = { 'action': 'my_action' };
    jQuery.post(my_ajax_url, data, function(response) {
    alert('This is from PHP: ' + response);
    });
    });
    wp_send_json_success()
    wp-includes/functions.php
    {
    success: true,
    data: $output_data
    }
    

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41. wp_send_json_error()
    Send a JSON response back to an Ajax request,
    indicating failure.
    wp-includes/functions.php
    wp_send_json()
    Send a JSON response back to an Ajax request.
    

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42. Where do I start?
    

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43. /wp-includes/general-template.php
    Mostly template tags.
    /wp-includes/functions.php
    Functions, functions everywhere.
    

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44. /wp-includes/formatting.php
    Strings, dates, and general formatting functions.
    /wp-includes/pluggable.php
    Overwritable functions. You can be creative, here
    (if you know what you are doing).
    

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45. Developer reference
    https://developer.wordpress.org/reference/
    

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46. PHP xref
    http://phpxref.ftwr.co.uk/wordpress/
    

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47. wpseek
    http://wpseek.com/
    

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48. Try to find these functions:
    wp_list_pluck()
    wp_list_filter()
    wp_extract_urls()
    make_clickable()
    add_query_arg()
    _split_str_by_whitespace()
    wp_remote_get()
    wp_parse_id_list()
    

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50. grazie.
    

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51. grazie.
    Domande?
    

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52. Earth image
    http://www.desy.de/information__services/press/press_releases/2013/pr_071113/index_eng.html
    

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