Sub groups ? - Programming structure...

Hello, - I'm used (in years gone by) to the Qbasic programme, where i can create 'sub' routines, & view each routine on its own - Without reference / Viewing the other code.. (I think its good like that..).. I know in CGI/Perl - you can use sub-routines etc... 1) Does PHP allow sub-routines, eg - I can send values to the routine, & it processes it & does whatever it requires & returns to the spot where I called it from. 2) For those of you that know Qbasic & know what i mean, is/are there any programmes out there that can allow you to view / see any sub-routines in Perl and/or PHP one at a time, & list them .. (I hope so) - Good, but not necessary.. G. (time for bed).