PHP upgrade killed my code- HELP

[joe_theschgroup]

I run a web site hosted remotely. Over the weekend they upgraded to version 4.1.2 for security reasons.
my programs bomb out with odd messages such as:
unknown Call to undefined function: key_exists()
Is there a list of functions that are now invalid ?
Are there any documented work-arounds?

[stolzyboy]

try

array_key_exists()

instead of

key_exists()

it was renamed

[joe_theschgroup]

Thanks, are there any more of these surprizes?