ereg/preg with large files

[Anon]

Hi,
This sounds like something that has already been discussed.
But since I didn't find it...
I would like to do ereg/preg on some potentially long files (i.e. several Meg long),
with the intent of identifying where the matches are (with the intent of replacement).
Should I just do $myText = fread ($fileHandle, filesize($fileName)) and then do
the match on $myText or is there a better way.
The intent of the question is to find out whether PHP will efficiently the temporary file that it should be creating behind the scenes or whether there is another solution that I should be using.

    Thanks for any comments
    Csaba Gabor