string / array format convert with php

问题:

i'm manually reading out database entries from a plugin (eventscalendar wordpress). there are user defined fields / custom fields stored in the database. excuse my ignorance - but i'm having trouble associating the format the data is stored in:

a:1:{s:3:"key";s:6:"extern";}

so in the end all i would need is the value of s:6:"" in a simple variable. lets say $key = "extern"

any quick solutions? thanks, mark