What is function name to trim string to certain length?

[my_filthy_mind]

I'm wondering what the PHP function is to trim a string variable to a length of 5 characters.

I have a database field containing the date in the following format "mm/dd/yy" format but would like to only display on one of my pages that date in "mm/dd" format (hence trim it to 5 characters from the left).

Thanks in advance for the help.

[Pig]

substr()