remove from a string

Is there a function in PHP that will remove a blob from inside a
string. Similar to the substr() function, but instead of giving me the
string I want it to remove the string.

For example, I have the string "john goes running" I want to be able
to tell it to remove 5 characters starting at position 4, which would
get me "john running"

Thanks,
Received on Mon Oct 24 02:09:33 2005