srch is a regular expression, and string.indexOf() does not handle reg exp, only plain strings. Use string.search instead.
The + means one or more occurence.
d is just a d. \d is a digit (same as the character class [0-9])
. is any character. . is just the dot character
So: match 1 or more didigts, followed by a dot, followed by one or more digits.
And do have a look at PCRE in the php.net documentation. It will give you a good idea about how it works, what options there are etc.
