As I learned the existence of __halt_compiler, I tried to compact huge data into rarely used PHP file.
And I use the file in this way:

if (...statement of init matched...) {
  require('init.dat'); // It is *.dat since it contains binary data for __halt_complier
}

However, because require or include will include the file no matter the code is actually executed or not, the large amount of data will be processed.

After a few days' thinking, I finally came out with this idea which will execute require only when necessary:

if (...statement of init matched...) {
  eval("require('init.dat');");
}

Note that eval('?>'.file_get_contents('init.dat')); will NOT do because of the existence of __halt_compiler