Some notes on how this works:

• Parses the method name and the caller.
• These are stored in an array, with the caller as the first value and the method name as the second.
• Special cases like self, parent and $this are resolved.

For static methods, the caller is always a class name. For non-static methods, it may be the class name (if it was called by $this), or it may be a variable (like $wpdb), or it could be another expression (like get_instance()).

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