Apply suggestion made during PR review

- Swap "Valid" and "Invalid" blocks.
- Add periods to titles and make them more descriptive.
- Highlight class instantiation, not method calls.
- Fix incorrect `$mysqli->query()` call that had extra argument.
- Change `{$wpdb->prefix}_posts` to `$wpdb->posts`.
- Remove trailing whitespace.
- Add trailing newline.
- Simplify standard description by removing "and methods".
- Fix indentation of <standard> description.

Author: rodrigoprimo

WordPress/Docs/DB/RestrictedClassesStandard.xml

@@ -1,67 +1,66 @@
 <?xml version="1.0"?>
 <documentation xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:noNamespaceSchemaLocation="https://phpcsstandards.github.io/PHPCSDevTools/phpcsdocs.xsd"
-    title="Restricted Database Classes and Methods"
+    title="Restricted Database Classes"
     >
     <standard>
     <![CDATA[
-      Avoid touching the database directly with PHP library classes and methods. Use the $wpdb object and associated functions instead.
+    Avoid touching the database directly with PHP library classes. Use the $wpdb object and associated functions instead.
     ]]>
     </standard>
     <code_comparison>
-        <code title="Invalid: Using the object-orientated mysqli interface">
+        <code title="Valid: Using a WordPress function to fetch posts.">
         <![CDATA[
-$mysqli = new mysqli(
-    "example.com", 
-    $db_user, 
-    $db_pass, 
-    $db_name 
-);
-
-$result = <em>$mysqli->query</em>(
-    $mysqli,
-    "SELECT * FROM wp_posts LIMIT 5" 
-);
-        ]]>
-        </code>
-        <code title="Valid: Use WordPress functions">
-        <![CDATA[
-$result = <em>get_posts()</em>;
+$results = <em>get_posts()</em>;
         ]]>
         </code>
-    </code_comparison>
-    <code_comparison>
-        <code title="Invalid: Using the object-orientated PDO and PDOStatement interfaces to insert a post">
+        <code title="Invalid: Using the mysqli class to fetch posts.">
         <![CDATA[
-$pdo   = new PDO( 
-    $dsn, 
-    $db_user, 
-    $db_pass 
+$mysqli = <em>new mysqli</em>(
+    'localhost',
+    $user,
+    $pass,
+    $db
 );
 
-$stmnt = $pdo->prepare(
-    "INSERT INTO wp_posts (post_title)
-    VALUES (?)" 
+$results = $mysqli->query(
+    "SELECT * FROM wp_posts LIMIT 5"
 );
-
-$stmnt->execute( ['Title'] );
         ]]>
         </code>
-        <code title="Valid: Use WordPress functions">
+    </code_comparison>
+    <code_comparison>
+        <code title="Valid: Using WordPress functions to insert a post.">
         <![CDATA[
-<em>wp_insert_post</em>( 
+<em>wp_insert_post</em>(
     array( 'post_title' => 'Title' )
 );
 
 // or...
 
 global $wpdb;
-<em>$wpdb->insert</em>( 
-    "{$wpdb->prefix}_posts",
+<em>$wpdb->insert</em>(
+    $wpdb->posts,
     array( 'post_title' => 'Title' ),
-    array( '%s' ) 
+    array( '%s' )
+);
+        ]]>
+        </code>
+        <code title="Invalid: Using PDO class to insert a post.">
+        <![CDATA[
+$pdo = <em>new PDO</em>(
+    $dsn,
+    $user,
+    $pass
 );
+
+$stmt = $pdo->prepare(
+    "INSERT INTO wp_posts (post_title)
+    VALUES (?)"
+);
+
+$stmt->execute( array( 'Title' ) );
         ]]>
         </code>
     </code_comparison>
-</documentation>
+</documentation>