Stripping Chars from a string

[Anon]

Hey guys
my problem is as follows
i want to start with a user defined string, such as:
$string1 = "hdghd543shsh";
but i want to remove all of the text characters from it leaving only the integers:

$string1 = "543";

Is this possible??

[yelvington]

$string = ereg_replace('[^{0-9]*','',$string);}

This says "find any character or characters that are not in the set 0 through 9, and replace with nothing."