$re = '/(?|^(\w+)|\w+\sPTR\s\[rip\+[^\],]+\](?=.*#\s0x0*([a-f0-9]+))|(\w+\sPTR\s\[[^\],]+\])|(?<!#\s)0x([a-f0-9]*)|(?<!#\s)(?|,(\w+)|(\w+),))/';
$str = 'movss xmm0,DWORD PTR [rip+0xd4],0x0000000000400978,eax,0x0,DWORD PTR [rbp-0x4] # 0x0000000000400c08
';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php