performance-issue with different mysql-approaches?

Hello,

is performance/ressource an issue if I use different kinds of
mysql-connections at the same time?

To explain: First I developed with native mysql_*() functions, then came
PEAR, which uses different DB-abstraction layers. But they do all use
mysql_*() at last, don't they?

So do I get mysql connections in parallel with my simultanouse use of
native php-mysql functions and pear packages using different (DB, MDB,
Adodb) abstraction layers?

Of course more ressources for the instances of classes are needed, sure,
but what about mysql-connections?

Thanks in advance and all the best
André