replace_string - replace all instances of a string within a string

string replace_string( string str, string pattern, string replace );

string replace_string( string str, string pattern, string replace, int max );

string replace_string( string str, string pattern, string replace, int first, int last );

replace_string() returns 'str' with all instances of 'pattern' replaced with 'replace'. If 'pattern' has zero length then str is returned unmodified. If the resultant string would exceed the maximum string length then replace_string() returns an undefinedp(), non-stringp() value.

replace_string() can be used to remove characters from a string by specifying a pattern and a zero-length replace parameter. For example, replace_string(" 1 2 3 ", " ", "") would return "123". replace_string() executes faster this way then explode()/implode().

The 4th and 5th arguments are optional (to retain backward compatibility.) The extra arguments have the following effect:

With 4 args:

The 4th argument specifies the maximum number of replacements to make (the count starts at 1). A value of 0 implies 'replace all', and thus, acts as replace_string() with 3 arguments would. E.g., replace_string("xyxx", "x", "z", 2) would return "zyzx".

With 5 args:

The 4th and 5th arguments specify the range of matches to replace between, with the following constraints:

first < 1 : change all from the start.
last == 0, or last > max_matches : change all to end
first > last : return the unmodified array.

E.g., replace_string("xyxxy", "x", "z", 2, 3) returns "xyzzy".