无法在php中的静态方法中使用self

Question

I can't use self in a static method , it gives me this error message : Fatal error: Using $this when not in object context in C:\\xampp\\htdocs\\wordpress\\wp-content\\plugins\\dw-usercp\\usercp.php on line 136

here is the source code :

class dw_usercp
{
    public static function plugin_activated() {
        self::create_plugin_pages();
    }

    public function create_plugin_pages() {
        $pages = array(
            'signin' => array(
                'title' => __( 'Sign In', 'dw-usercp' ),
                'content' => '[dwusercp-sigin-form]',
                'option_id' => 'login_page'
            ),
            'user-account' => array(
                'title' => __( 'Your Account', 'dw-usercp' ),
                'content' => '[dwusercp-info]',
                'option_id' => 'user_account_page'
            ),
            'edit-user-info' => array(
                'title' => __( 'Edit User Info', 'dw-usercp' ),
                'content' => '[dwusercp-edit-info]',
                'option_id' => 'user_editinfo_page'
            ),
            'profile' => array(
                'title' => __( 'User profile', 'dw-usercp' ),
                'content' => '[dwusercp-profile]',
                'option_id' => 'profile_page'
            ),
            'signup' => array(
                'title' => __( 'Sign Up', 'dw-usercp' ),
                'content' => '[dwusercp-signup-form]',
                'option_id' => 'register_page'
            ),
            'user-lost-password' => array(
                'title' => __( 'Forgot Your Password?', 'dw-usercp' ),
                'content' => '[dwusercp-password-lost-form]',
                'option_id' => 'lost_password_page'
            ),
            'user-password-reset' => array(
                'title' => __( 'Pick a New Password', 'dw-usercp' ),
                'content' => '[dwusercp-password-reset-form]',
                'option_id' => 'password_reset_page'
            )
        );

        foreach( $pages as $slug => $page ) {
            $query = new WP_Query( 'pagename=' . $slug );
            if ( ! $query->have_posts() ) {
                // Add the page using the data from the array above
                $post_id = wp_insert_post(
                    array(
                        'post_content'   => $page['content'],
                        'post_name'      => $slug,
                        'post_title'     => $page['title'],
                        'post_status'    => 'publish',
                        'post_type'      => 'page',
                        'ping_status'    => 'closed',
                        'comment_status' => 'closed',
                    )
                );

                $this->update_plugin_option( $page['option_id'], $post_id ); // this is the line 136 that the error message says
            }
        }
    }

    /**
     * Update plugin option
     * 
     * @param string $field option id
     * @param mixed $value option new value
     * @return bool
     */
    public function update_plugin_option( $field, $value ) {
        $options = get_option("dw_usercp_options");
        $options[$field] = $value;

        update_option( "dw_usercp_options", $options );
    }
}
$dw_usercp = new dw_usercp();

register_activation_hook( __FILE__, array( 'dw_usercp', 'plugin_activated' ) );

how do i call the create_plugin_pages() correctly then?

the plugin_activated() has to be static as Wordpress says

Answer 1

Inside a static function, you're not in an instance of the class. You could:

• instantiate an instance of the class and call the function
• Pass an instatiated object into the static funtion
• Make the create_plugin_pages function static and call it with static.
• Convert plugin_activated to not be static (MY VOTE)

The static option won't work though since you call $this inside create_plugin_pages . So you'll need to go the instatiation route.

Non-static

  public function plugin_activated() {
       $this->create_plugin_pages();
   }

Here's the passing in an object version

   public static function plugin_activated(dw_usercp $a_dw_usercp) {
       $a_dw_usercp->create_plugin_pages();
   }

Answer 2

Its because you are using "$this" variable when you're in static context (did you read the error message?)

When in static context, use for methods:

self::method(args) ;

or

self::$attr for variables (attributes)

Answer 3

$this->update_plugin_option( $page['option_id'], $post_id );

is not self , as referenced in your title. You should be using:

self::update_plugin_option( $page['option_id'], $post_id );