WPMU New Blog Template: Protect a page from editing in site created using a template

code.php

<?php

add_action( 'init', 'is_nbt_enabled' );
add_filter( 'page_row_actions', 'remove_page_row_actions', 10, 2 );
add_filter( 'get_sample_permalink_html', 'remove_edit_permalink', 10, 2 );
add_filter( 'admin_body_class', 'admin_body_class' );
add_filter( 'user_has_cap', 'lock_deletion', 0, 3 );

function is_nbt_enabled() {
    if( defined( 'NBT_PLUGIN_VERSION' ) ){
        if( is_super_admin() ){
            add_action( 'add_meta_boxes', 'nbp_protect_page' );
        }
    }
}

function nbp_protect_page() {
    add_meta_box( 'protect_page', 'Protect This Page', 'protect_page_cb', 'page', 'side', 'high' );
}

function protect_page_cb( $post ) {
    wp_nonce_field( 'nbpt_save_meta_box_data', 'nbpt_meta_box_nonce' );
    $value = get_post_meta( $post->ID, '_nbpt_meta_value_key', true );
    ?>
    <label for="protect_page">Protect this page from editing?</label><br><br>
    <input <?php echo isset( $value ) && $value == 1 ? 'checked' : '' ?> type="radio" name="protect_page" value="1"> Yes
    <input <?php echo ! isset( $value ) || $value == 0 ? 'checked' : '' ?> type="radio" name="protect_page" value="0"> No
    <?php
}

add_action( 'save_post', 'nbpt_save_meta_box_data' );
function nbpt_save_meta_box_data( $post_id ) {
    if ( ! isset( $_POST['nbpt_meta_box_nonce'] ) ) {
	return;
    }
    if ( ! wp_verify_nonce( $_POST['nbpt_meta_box_nonce'], 'nbpt_save_meta_box_data' ) ) {
        return;
    }
    if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
        return;
    }
    if( ! is_super_admin() ){
        return;
    }
    update_post_meta( $post_id, '_nbpt_meta_value_key', $_POST['protect_page'] );
}

function is_locked( $post = 0 ){
    if( ! is_object( $post ) ){
        if( $post == 0 ) {
            global $post;
            $post_id = $post->ID;
        }else{
            $post_id = $post;
        }
    }else{
        $post_id = $post->ID;
    }
    $value = get_post_meta( $post_id, '_nbpt_meta_value_key', true );
    return ( isset( $value ) && $value == 1 ) && ! is_super_admin();
}

function remove_page_row_actions( $actions, $post ) {
    if( is_locked( $post ) ) {
        foreach ( array( 'inline', 'inline hide-if-no-js', 'trash', 'edit' ) as $action_key ) {
            if ( array_key_exists( $action_key, $actions ) ) {
                unset ( $actions[ $action_key ] );
            }
        }
    }
    return $actions;
}

function remove_edit_permalink( $html, $post_id ) {
    if( is_locked( $post_id ) ) {
        $element_start	= strpos( $html, '<span id="edit-slug-buttons"' );
        $element_end	= strpos( $html, '</span>', $element_start ) + 8;
        $html			= substr_replace( $html, '', $element_start, $element_end - $element_start );
        $html			= preg_replace( '#<span id="editable-post-name"[^>]*>([^<]+)</span>#', '$1', $html );
    }
    return $html;
}

function admin_body_class( $class ) {
    if( is_locked() ) {
            $class .= ' page-locked';
    }
    return $class;
}

function lock_deletion( $allcaps, $caps, $args ) {
    $cap_check	= count( $args ) ? $args[0] : '';
    $user_id	= count( $args ) > 1 ? $args[1] : 0;
    $object_id	= count( $args ) > 2 ? $args[2] : 0;
    
    if( is_locked() ) {
            foreach( $allcaps as $cap => $value ) {
            if ( strpos( $cap, "delete_" ) !== false || strpos( $cap, "edit_" ) !== false ) {
                unset( $allcaps[ $cap ] );
            }
        }
    }
    
    return $allcaps;
}