How to create a Custom Meta Box with Name/Value Admin User Input Fields?

Question

I have researched many tutorials on how to create/add Custom Meta Boxes using the add_meta_box() Wordpress function. I can not find any example where the finished Meta Box has the option for an Admin User to input both key/value pairs like Custom_Fields?

EDIT: Removed plugin link URL as not enough rep points:

I want to add this capability to my own Custom Meta Boxes and to the WebDevStudios/Custom-Metaboxes-and-Fields-for-WordPress plugin's Meta Box fields.

To clarify, I want to create a Meta Box that Admin Users can add Name and Value to - like is shown in this image taken from the WP's own Custom Fields Meta Box :

Edit 19.06.14:

My understanding of Custom Fields was incorrect, when querying on the front end:

        printf( '<pre>%s</pre>', var_export( get_post_meta($post->ID,"my_custom_filed_key"), true ) );

I see that my_custom_field_key produces an index array:

array (
0 => 'val  1',
1 => 'val  2',
2 => 'val  3',
)

I suppose what I am trying to achieve is an associative array?

array (
'my key name 1' => 'my val 1',
'my key name 2' => 'my val 2',
'my key name 3' => 'my val 3',
)

Here is the add_meta_box function part of my code:

function my_meta_boxes($post) {
        add_meta_box(
            'my_meta',          // Unique ID
            esc_html__( 'Reviews', 'example' ), // Title
            'my_meta_box',  // Callback function
            'my-post',          // Admin page (or post type)
            'side',               // Context
            'default'             // Priority
        );
 }

/* Display the post meta box. */
function my_meta_box() { 
        wp_nonce_field( basename( __FILE__ ), 'my_post_nonce' ); 

        $meta = get_post_custom($post->ID);
        $meta['my_meta'] = maybe_unserialize($meta['my_meta'][0]);
        ?>
        <table style="width:100%;">
                <tr style="width:100%;">
                <td><textarea style="width:90%;" rows="1" name="my_meta[]"> <?php echo $meta['my_meta'][0] ?></textarea></td>
                </tr>
                <tr style="width:100%;">
                <td><textarea style="width:90%;" rows="1" name="my_meta[]"> <?php echo $meta['my_meta'][1] ?></textarea></td>
                </tr>
                <tr style="width:100%;">
                <td><textarea style="width:90%;" rows="1" name="my_meta[]"> <?php echo $meta['my_meta'][2] ?></textarea></td>
                </tr>
        </table>
<?php }

I am wondering if the add_meta_box $callbacks_args would help me here, but I am yet to full understand it?

Thank you.

Answer 1

To help you understanding how forms work: They add to the $_POST array by a form fields name argument.

<input type="text" name="foo" value="Fooo!" />

would produce

$_POST (array) =>
    foo => Fooo!

while

<input type="text" name="foo[bar]" value="Bar." />
<input type="text" name="foo[baz]" value="Baz." />

would produce

$_POST (array) =>
    foo => (array) =>
        bar => Bar.
        baz => Baz.

and so on.