This function is identical to ereg_replace() except that this ignores case distinction when matching alphabetic characters.
Parameters
pattern
A POSIX extended regular expression.
replacement
If pattern contains parenthesized substrings, replacement 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.
string
The input string.
Return Values
The modified string is returned. If no matches are found in string , then it will be returned unchanged.