Modifying strings in place

[Anon]

I have a very long string which I am building (>1Meg), and I have cause to repeatedly modify varying bytes (characters) of the string. To avoid massive amounts of needless copying, I would like to do an in place modification of the string rather than using substr_replace, which will return a copy. Is there any way to accomplish this?
I.e. inPlaceModify ($SourceStr, $Position, $ReplacementChar)

 Thanks,
        Csaba

[brandonschnell]

just roll your own version of the substr_replace function but rather then returning a copy of the string, pass a pointer to the string to a function along with the text to replace, treat the pointer as a long array ($str[pos]) looking for the text to replace. it'll be slow because it has to scan the entire string, but not much slower i would assume then any other str replace function.