This function is identical to ereg_replace()
except that this ignores case distinction when matching
A POSIX extended regular expression.
contains parenthesized substrings,
may contain substrings of the form
\\digit, which will be
replaced by the text matching the digit'th parenthesized substring;
\\0 will produce the entire contents of string.
Up to nine substrings may be used. Parentheses may be nested, in which
case they are counted by the opening parenthesis.
The input string.
The modified string is returned. If no matches are found in
, then it will be returned unchanged.