SublimeText: replace "this" with "$this->" when typing in PHP files

thisphp.py

import sublime
import sublime_plugin

class PhpThisToThisArrowCommand(sublime_plugin.TextCommand):
    def run(self, edit):
        # Get the current cursor position
        for region in self.view.sel():
            if region.empty():
                # Get the position of the cursor
                pos = region.begin()

                # Ensure we do not attempt to create a negative region
                if pos < 5:
                    continue

                # Check if "this." is before the cursor
                word_region = sublime.Region(pos - 5, pos)
                word = self.view.substr(word_region)

                if word == "\tthis":
                    # Replace "[tab]this" with "[tab]$this->"
                    self.view.replace(edit, word_region, "\t$this->")
                elif word == " this":
                    # Replace "[space]this." with "[space]$this->"
                    self.view.replace(edit, word_region, " $this->")

class PhpThisToThisArrowListener(sublime_plugin.EventListener):
    def on_modified_async(self, view):
        # Check if the current file is a PHP file
        if view.is_valid() and len(view.sel()) > 0 and view.match_selector(view.sel()[0].begin(), "source.php"):
            view.run_command("php_this_to_this_arrow")

To be put in ~/Library/Application Support/Sublime Text/Packages/User