string str_replace(string needle, string str, string haystack);
This function replaces all occurences of needle in haystack with the given str. If you don't need fancy replacing rules, you should always use this function instead of ereg_replace().
Example 1. str_replace() example
$bodytag = str_replace("%body%", "black", "<body text=%body%>");
This function is binary safe.
str_replace() was added in PHP 3.0.6, but was buggy up until PHP 3.0.8.