Parsekit has parsekit_compile_string().
sudo pecl install parsekit
var_dump(parsekit_compile_string(<<The output is quite verbose, so you'd need to process it to get assembler-like format.
["opcodes"]=> array(10) { [0]=> array(9) { ["address"]=> int(44682716) ["opcode"]=> int(101) ["opcode_name"]=> string(13) "ZEND_EXT_STMT" ["flags"]=> int(4294967295) ["result"]=> array(8) { ["type"]=> int(8) ["type_name"]=> string(9) "IS_UNUSED" ["var"]=> int(0) ["opline_num"]=> string(1) "0" ["op_array"]=> string(1) "0" ["jmp_addr"]=> string(1) "0" ["jmp_offset"]=> string(8) "35419039" ["EA.type"]=> int(0) } ["op1"]=> array(8) { ["type"]=> int(8) ["type_name"]=> string(9) "IS_UNUSED" ["var"]=> int(0) ["opline_num"]=> string(1) "0" ["op_array"]=> string(1) "0" ["jmp_addr"]=> string(1) "0" ["jmp_offset"]=> string(8) "35419039" ["EA.type"]=> int(0) }