Remember that methods are also called functions in PHP. The only difference is that a method is used within a class and a function is used by itself.<\/em><\/p>\nI\u2019ll explain this in a bit more detail in a second. But first, let\u2019s go ahead and stick this new $wpdb tool into our class.\u00a0 Assuming that we\u2019re working with the two tables I showed you above and see if you can figure out whose data I\u2019m accessing with this method:<\/p>\n
{code type=php}<\/p>\n
function BestAuthor() {<\/p>\n
global $wpdb;<\/p>\n
$user_data = $wpdb->get_row(\u201cSELECT first_name, last_name FROM $wpbd->users WHERE id = \u20181\u2019);<\/p>\n
echo $user_data[\u2018first_name\u2019];<\/p>\n
}<\/p>\n
<\/code><\/p>\n
If you call this function later within your class handler, it will echo out the name \u201cJack.\u201d Of course, this example won\u2019t work if you try it on your WordPress test site because the WordPress database tables are different than the ones we\u2019re using in this post. But this example is just for the sake of making the concept simple to grasp.<\/p>\n
Let\u2019s break down each line of this method in plain English so you can see what we\u2019ve actually done. First, we created a new method and named it \u201cBestAuthor.\u201d<\/p>\n
{code type=php}<\/p>\n
function BestAuthor() {<\/p>\n
<\/code><\/p>\n
Then, we defined exactly what this method would do by enclosing some code between the { and the } characters. First, we called the $wpdb variable as a \u201cglobal,\u201d letting WordPress know that we were going to work with the \u201c$wpdb\u201d\u2019 class:<\/p>\n
{code type=php}<\/p>\n
function BestAuthor() {<\/p>\n
global $wpdb;<\/p>\n
<\/code><\/p>\n
BTW, \u201cGlobal\u201d simply means that the variable can be used anywhere within the WordPress install, rather than being good only within a function or a class itself. Since $wpdb has been defined in WordPress as a global, we call it as a global.<\/p>\n
Once we\u2019ve closed that line with the \u201c;\u201d character, we create a variable called \u201c$user_data\u201d and store some information within that variable just as I explained in the first post of this series. However, this time we used a few commands to grab Jack\u2019s data from within the \u201cuser\u201d table within our database.<\/p>\n
Let\u2019s look at those commands again and see if you can spot how we asked for Jack\u2019s data:<\/p>\n
{code type=php}<\/p>\n
$wpdb->get_row(\u201cSELECT first_name, last_name FROM $wpbd->users WHERE id = \u20181\u2019);<\/p>\n
echo $user_data[\u2018first_name\u2019];<\/p>\n
<\/code><\/p>\n
The \u201c$wpdb\u201d shows that we\u2019re using the WordPress database toolbox to select a row (get_row) within our database. We then \u201cSELECT\u201d the \u201cfirst_name\u201d and the \u201clast_name \u201c records \u201cFROM\u201d the table named \u201cusers\u201d (once again, using the \u201c$wpdb\u201d tool to access the database \u201cWHERE\u201d the \u201cid\u201d is equivalent to \u201c1.\u201d<\/p>\n
If you look at our users table again, you\u2019ll notice that Jack\u2019s id is equivalent to one, so we just grabbed Jack\u2019s first and last name out of that table. Then, the last line simply echoes out the \u201c[\u2018first_name\u2019]\u201d segment of our \u201c$user_data\u201d variable. If I\u2019d wanted to echo the last name as well, I would have simply added another line which reads:<\/p>\n
echo $user_data[\u2018last_name\u2019];<\/strong><\/p>\nWhat if I\u2019d wanted to display Jack\u2019s email as well?<\/p>\n
No problem, just add another line right?<\/p>\n
echo $user_data[\u2018email\u2019];<\/strong><\/p>\nAh, but not quite.<\/p>\n
Check out our \u201c$user_data\u201d array (variables which contain strings of information are called \u201carrays\u201d) and you\u2019ll notice that we didn\u2019t ask the WordPress database for the user\u2019s email. So that echo command wouldn\u2019t give us any information. To get the result we\u2019re looking for, we\u2019d need to update our \u201cget_row\u201d function to request that data as well:<\/p>\n
{code type=php}<\/p>\n
$wpdb->get_row(\u201cSELECT * FROM $wpbd->users WHERE id = \u20181\u2019);<\/p>\n
echo $user_data[\u2018first_name\u2019];<\/p>\n
<\/code><\/p>\n
That \u201c*\u201d character tells the WordPress database that I want to select everything from the users database where the column \u201cid\u201d is equal to the integer \u20181\u2019. If I\u2019d wanted to select the data based on the user\u2019s email instead of based on their id, I\u2019d rewrite my code to read like this:<\/p>\n
{code type=php}<\/p>\n
$wpdb->get_row(\u201cSELECT * FROM $wpbd->users WHERE email = \u2018jacksemail@url.com\u2019);<\/p>\n
echo $user_data[\u2018first_name\u2019];<\/p>\n
<\/code><\/p>\n
This code ^ could be used to discover a user\u2019s name if you only have their email to work with. With this information, I could then search out other <\/em>data within my database base which was either created by the user or which related to their user account.<\/p>\nNow, we won\u2019t actually be making your WordPress Basic plugin do anything yet because it\u2019s important to understand this concept first. So let\u2019s take a few code examples and see if you can figure out what we\u2019re doing with these\u2026<\/p>\n
Test Your New Knowledge of WordPress Database Theory<\/h2>\n
![\"Post](\"https:\/\/wpmudev.com\/blog\/wp-content\/uploads\/2012\/08\/test-your-knowledge.jpg\")
<\/p>\n
Rather than just giving you the answer to these methods, I\u2019m going to ask you to leave your guesses in the comments below this blog post. Keep in mind \u00a0that we\u2019re grabbing information from the fictional database tables from earlier in this post:<\/p>\n
Method #1:<\/strong><\/p>\n{code type=php}<\/p>\n
function BlogTitle() {<\/p>\n
global $wpdb;<\/p>\n
\/\/grab post data\/\/<\/p>\n
$post_data = $wpdb->get_row(\u201cSELECT * FROM $wpbd->post_content WHERE id = \u20181\u2019);<\/p>\n
$post_title = $post_data[\u2018title\u2019];<\/p>\n
echo $post_title;<\/p>\n
}<\/p>\n
<\/code><\/p>\n
Method #2:<\/strong><\/p>\n{code type=php}<\/p>\n
function BlogAuthor() {<\/p>\n
global $wpdb;<\/p>\n
\/\/grab post data\/\/<\/p>\n
$post_data = $wpdb->get_row(\u201cSELECT * FROM $wpbd->post_content WHERE id = \u20181\u2019);<\/p>\n
$author_id = $post_data[\u2018author_id\u2019];<\/p>\n
\/\/grab and display author name\/\/<\/p>\n
$author_name = $wpdb->get_row(\u201cSELECT first_name FROM $wpbd->users WHERE id = \u2018$author_id\u2019);<\/p>\n
echo $author_name[\u2018first_name\u2019];<\/p>\n
}<\/p>\n
<\/code><\/p>\n
Method #2:<\/strong><\/p>\n{code type=php}<\/p>\n
function AuthorEmail () {<\/p>\n
global $wpdb;<\/p>\n
\/\/grab post data\/\/<\/p>\n
$post_data = $wpdb->get_row(\u201cSELECT * FROM $wpbd->post_content WHERE id = \u20181\u2019);<\/p>\n
$author_id = $post_data[\u2018author_id\u2019];<\/p>\n
\/\/grab and display author name and email\/\/<\/p>\n
$author_data = $wpdb->get_row(\u201cSELECT first_name, email FROM $wpbd->users WHERE id = \u2018$author_id\u2019);<\/p>\n
echo $author_data[\u2018first_name\u2019];<\/p>\n
echo \u201c \u201c . $author_data[\u2018last_name\u2019];<\/p>\n
echo \u201c \u201c . $author_data[\u2018email\u2019];<\/p>\n
}<\/p>\n
<\/code><\/p>\n
If you can guess what each of these methods will echo out, you\u2019re ready to start giving your WordPress plugin a memory using the $wpdb class. Let\u2019s see how you do, post your responses below!<\/p>\n
-Till next time,<\/p>\n
Seth C<\/p>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
This tutorial series requires no programming experience, you’ll simply learn how to build a WordPress plugin from scratch…<\/p>\n","protected":false},"author":132058,"featured_media":94533,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"blog_reading_time":"","wds_primary_category":0,"wds_primary_tutorials_categories":0,"footnotes":""},"categories":[263],"tags":[131],"tutorials_categories":[],"class_list":["post-94529","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-tutorials","tag-developers"],"_links":{"self":[{"href":"https:\/\/wpmudev.com\/blog\/wp-json\/wp\/v2\/posts\/94529","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wpmudev.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/wpmudev.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/wpmudev.com\/blog\/wp-json\/wp\/v2\/users\/132058"}],"replies":[{"embeddable":true,"href":"https:\/\/wpmudev.com\/blog\/wp-json\/wp\/v2\/comments?post=94529"}],"version-history":[{"count":0,"href":"https:\/\/wpmudev.com\/blog\/wp-json\/wp\/v2\/posts\/94529\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/wpmudev.com\/blog\/wp-json\/wp\/v2\/media\/94533"}],"wp:attachment":[{"href":"https:\/\/wpmudev.com\/blog\/wp-json\/wp\/v2\/media?parent=94529"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/wpmudev.com\/blog\/wp-json\/wp\/v2\/categories?post=94529"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/wpmudev.com\/blog\/wp-json\/wp\/v2\/tags?post=94529"},{"taxonomy":"tutorials_categories","embeddable":true,"href":"https:\/\/wpmudev.com\/blog\/wp-json\/wp\/v2\/tutorials_categories?post=94529"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
![\"Post](\"https:\/\/wpmudev.com\/blog\/wp-content\/uploads\/2012\/08\/memory-loss.jpg\")
<\/p>\n![\"Post](\"https:\/\/wpmudev.com\/blog\/wp-content\/uploads\/2012\/08\/user-table.jpg\")
<\/a><\/p>\n![\"Post](\"https:\/\/wpmudev.com\/blog\/wp-content\/uploads\/2012\/08\/content-table.jpg\")
\u00a0<\/strong><\/p>\n