You are looking for custom meta boxes, with the add_meta_box() function:
Adds a meta box to one or more screens.
And the add_meta_boxes action hook.
Fires after all built-in meta boxes have been added:
A simple example would be if we wanted to add a "Listening to..." custom meta box, to share our mood while writing a post.
<?php
add_action( 'add_meta_boxes', 'add_meta_listening_to' );
function add_meta_listening_to() {
add_meta_box(
'meta_listening_to', //id
'Listening to ...', //title
'listeningto', //callback
'post', //screen &/or post type
'normal', //context
'high', //priority
null //callback_args
);
};
function listeningto( $post ) { //function handle same as callback
$ListeningToInput = get_post_meta( $post->ID, 'ListeningToInput', true );
echo '<input name="listening_to_input" type="text" placeholder="Listening to ..." value="'. $ListeningToInput .'" style="width:100%;">';
};
add_action( 'save_post', 'save_meta_listening_to' );
function save_meta_listening_to( $post_ID ) {
if ( isset( $_POST[ 'listening_to_input' ] ) ) {
update_post_meta( $post_ID, 'ListeningToInput', esc_html( $_POST[ 'listening_to_input' ] ) );
};
}; ?>
Then to display on the front end, we would use the following:
<?php echo get_post_meta( $post->ID, 'ListeningToInput', true ); ?>
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