PHP can't do this out of the box. You'd need to install the xDebug extension on your PHP development machine. Once installed, you could use the code coverage function to determine which lines have executed.
Lacking that, I'd create a simple debug function to include at the top of your code
public function myDebugString($string)
{
file_put_contents('/tmp/debug.log',"$string\n",FILE_APPEND);
return;
}
and then add calls to this throughout you code
myDebugString('Called at ' . __LINE__);
And then tail the log file created. Removing the debug statements is a simple find/replace operation for your editor once you're done.
Many frameworks have debugging objects that do way more than this built it, but if you're dealing with stand alone code something simple like this should be enough to get you by.