Polyglot for C and PHP

I was thinking of a compiler that spits out C/PHP polyglots, but not sure if possible. Main issue is the PHP opening/closing brackets, <?php and ?>. I wanted to make them as macros that expand to nothing, but macros can't have such identifiers. Any way around this?

#define <?php
#define ?>
#define $

The polyglot does not need to be readable, semi-readable is good enough. Thankful for any feedback!

Solution

One small example:

//<?php echo "\x08\x08"; ob_start(); ?>
#include <stdio.h>
#define function 

int
// <?php
function main(int $x)
{
    printf("Hello %d\n", $x);
}

// ?>
// <?php ob_end_clean(); main(1);

And with C syntax highlight (but same piece of code):

//<?php echo "\x08\x08"; ob_start(); ?>
#include <stdio.h>
#define function 

int
// <?php
function main(int $x)
{
    printf("Hello %d\n", $x);
}

// ?>
// <?php ob_end_clean(); main(1);

Edit: Well the int function type won't work. Right now, I'm using #__C__ prefix on such lines, and then sed to remove it before compiling. So not 100% polyglot, sadly. ^^