you must find and set those three php error settings in the php.ini on your system, because -
your main code file never runs upon a php syntax error, so putting the settings in your code won't do anything for this type of error.
the display_startup_errors setting does nothing when in your php code because php has already started.
while you are changing settings in the php.ini, find the output_buffering setting and set it to OFF. php's output buffering should only be used when you want to buffer output and it being on hides non-fatal php errors and any output from your code when you have header statements in your code.
by putting these in the php.ini, you have one location where you can change them and you don't need to edit any code when you move your project to a live/public server.
stop and start your web server to get any changes made to the php.ini to take effect and then use a phpinfo() statement in a .php script that you open as a web page to conform that the settings actually got changed in case the php.ini that you are changing is not the one that php is using.