add meta box

1/**
2 * Calls the class on the post edit screen.
3 */
4function call_someClass() {
5    new someClass();
6}
7 
8if ( is_admin() ) {
9    add_action( 'load-post.php',     'call_someClass' );
10    add_action( 'load-post-new.php', 'call_someClass' );
11}
12 
13/**
14 * The Class.
15 */
16class someClass {
17 
18    /**
19     * Hook into the appropriate actions when the class is constructed.
20     */
21    public function __construct() {
22        add_action( 'add_meta_boxes', array( $this, 'add_meta_box' ) );
23        add_action( 'save_post',      array( $this, 'save'         ) );
24    }
25 
26    /**
27     * Adds the meta box container.
28     */
29    public function add_meta_box( $post_type ) {
30        // Limit meta box to certain post types.
31        $post_types = array( 'post', 'page' );
32 
33        if ( in_array( $post_type, $post_types ) ) {
34            add_meta_box(
35                'some_meta_box_name',
36                __( 'Some Meta Box Headline', 'textdomain' ),
37                array( $this, 'render_meta_box_content' ),
38                $post_type,
39                'advanced',
40                'high'
41            );
42        }
43    }
44 
45    /**
46     * Save the meta when the post is saved.
47     *
48     * @param int $post_id The ID of the post being saved.
49     */
50    public function save( $post_id ) {
51 
52        /*
53         * We need to verify this came from the our screen and with proper authorization,
54         * because save_post can be triggered at other times.
55         */
56 
57        // Check if our nonce is set.
58        if ( ! isset( $_POST['myplugin_inner_custom_box_nonce'] ) ) {
59            return $post_id;
60        }
61 
62        $nonce = $_POST['myplugin_inner_custom_box_nonce'];
63 
64        // Verify that the nonce is valid.
65        if ( ! wp_verify_nonce( $nonce, 'myplugin_inner_custom_box' ) ) {
66            return $post_id;
67        }
68 
69        /*
70         * If this is an autosave, our form has not been submitted,
71         * so we don't want to do anything.
72         */
73        if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
74            return $post_id;
75        }
76 
77        // Check the user's permissions.
78        if ( 'page' == $_POST['post_type'] ) {
79            if ( ! current_user_can( 'edit_page', $post_id ) ) {
80                return $post_id;
81            }
82        } else {
83            if ( ! current_user_can( 'edit_post', $post_id ) ) {
84                return $post_id;
85            }
86        }
87 
88        /* OK, it's safe for us to save the data now. */
89 
90        // Sanitize the user input.
91        $mydata = sanitize_text_field( $_POST['myplugin_new_field'] );
92 
93        // Update the meta field.
94        update_post_meta( $post_id, '_my_meta_value_key', $mydata );
95    }
96 
97 
98    /**
99     * Render Meta Box content.
100     *
101     * @param WP_Post $post The post object.
102     */
103    public function render_meta_box_content( $post ) {
104 
105        // Add an nonce field so we can check for it later.
106        wp_nonce_field( 'myplugin_inner_custom_box', 'myplugin_inner_custom_box_nonce' );
107 
108        // Use get_post_meta to retrieve an existing value from the database.
109        $value = get_post_meta( $post->ID, '_my_meta_value_key', true );
110 
111        // Display the form, using the current value.
112        ?>
113        <label for="myplugin_new_field">
114            <?php _e( 'Description for this field', 'textdomain' ); ?>
115        </label>
116        <input type="text" id="myplugin_new_field" name="myplugin_new_field" value="<?php echo esc_attr( $value ); ?>" size="25" />
117        <?php
118    }
119}
120

1function custom_meta_box_markup($object)
2{
3    wp_nonce_field(basename(__FILE__), "meta-box-nonce");
4
5    ?>
6        <div>
7            <label for="meta-box-text">Text</label>
8            <input name="meta-box-text" type="text" value="<?php echo get_post_meta($object->ID, "meta-box-text", true); ?>">
9
10            <br>
11
12            <label for="meta-box-dropdown">Dropdown</label>
13            <select name="meta-box-dropdown">
14                <?php 
15                    $option_values = array(1, 2, 3);
16
17                    foreach($option_values as $key => $value) 
18                    {
19                        if($value == get_post_meta($object->ID, "meta-box-dropdown", true))
20                        {
21                            ?>
22                                <option selected><?php echo $value; ?></option>
23                            <?php    
24                        }
25                        else
26                        {
27                            ?>
28                                <option><?php echo $value; ?></option>
29                            <?php
30                        }
31                    }
32                ?>
33            </select>
34
35            <br>
36
37            <label for="meta-box-checkbox">Check Box</label>
38            <?php
39                $checkbox_value = get_post_meta($object->ID, "meta-box-checkbox", true);
40
41                if($checkbox_value == "")
42                {
43                    ?>
44                        <input name="meta-box-checkbox" type="checkbox" value="true">
45                    <?php
46                }
47                else if($checkbox_value == "true")
48                {
49                    ?>  
50                        <input name="meta-box-checkbox" type="checkbox" value="true" checked>
51                    <?php
52                }
53            ?>
54        </div>
55    <?php  
56}