WordPress新手求助：排查PHP Notice: Trying to get property of non-object错误

Hey there! I totally get how frustrating that notice can be when you're starting out with PHP and WordPress—let's break down exactly what's causing it and how to fix it, since you've narrowed the issue down to your bee_security function hooked to template_redirect.

What's the root cause? #

This error pops up when your code tries to access a property (using the -> syntax) on something that isn't an object. Most often in WordPress, this happens because:

• You're assuming a global variable (like $post) exists and is an object, but it's actually null (e.g., on a 404 page, archive, or homepage where there's no single post/page object)
• You're using a function that might return false or null instead of an object (like get_user_by() if the user doesn't exist, or get_post() for an invalid post ID)
• The object you're trying to access hasn't been fully initialized yet when the template_redirect hook runs

Common fixes tailored to your code #

Let's walk through examples of how to fix the most likely issues in your bee_security function:

1. Checking if the global $post object exists before using it

If your code is trying to check the current page ID or post type, don't directly use $post->ID without verifying the object exists first.

Bad code (causes the notice):

function bee_security() {
    global $post;
    // No check if $post is actually an object
    if ( $post->ID != 123 ) { 
        wp_redirect( home_url() );
        exit;
    }
}
add_action('template_redirect', 'bee_security');

Fixed code:

function bee_security() {
    global $post;
    // First confirm $post is an object and has the ID property
    if ( isset( $post ) && is_object( $post ) && $post->ID != 123 ) { 
        wp_redirect( home_url() );
        exit;
    }
    // Even better: Use WordPress built-in conditionals which handle checks for you
    if ( !is_page( 123 ) ) {
        wp_redirect( home_url() );
        exit;
    }
}
add_action('template_redirect', 'bee_security');

2. Verifying function returns are objects before accessing properties

If your code uses functions like get_user_by() or similar that might return non-objects, always check the result first.

Bad code:

function bee_security() {
    $current_user = wp_get_current_user();
    // No check if user data is valid
    if ( $current_user->user_role != 'subscriber' ) {
        wp_redirect( home_url() );
        exit;
    }
}

Fixed code:

function bee_security() {
    $current_user = wp_get_current_user();
    // Check if we have a valid user object and the role property exists
    if ( is_object( $current_user ) && property_exists( $current_user, 'roles' ) && !in_array( 'subscriber', $current_user->roles ) ) {
        wp_redirect( home_url() );
        exit;
    }
}

3. Using more reliable WordPress functions

Instead of relying on global variables, use get_queried_object() which returns the current queried object (post, page, category, etc.) or null if none exists. It's often more reliable than the global $post in hooks like template_redirect:

function bee_security() {
    $queried_obj = get_queried_object();
    // Check if it's a page object before accessing its ID
    if ( is_object( $queried_obj ) && $queried_obj->post_type === 'page' && $queried_obj->ID != 123 ) {
        wp_redirect( home_url() );
        exit;
    }
}

Quick troubleshooting steps for your specific code #

1. Go through every line in your bee_security function where you use -> to access a property
2. For each one, add a check to confirm the variable is an object first (use is_object($var) and isset($var->property) to be safe)
3. Replace direct object property checks with WordPress built-in conditionals (like is_page(), is_single(), is_user_logged_in()) whenever possible—these functions already handle existence checks under the hood

That should squash that notice for you! If you can share the full code of bee_security, I can give even more targeted advice.

内容的提问来源于stack exchange，提问作者Aaron McKeon