Christopher Jones – PHP OCI8 Signal Handling and --enable-sigchild:

"Only if you see defunct "zombie" Oracle server processes then start PHP/Apache with the Oracle Net option BEQUEATH_DETACH=YES in your sqlnet.ora, or, to keep the setting specific to PHP, set your environment starting Apache.

[…] You should never need to configure PHP with --enable-sigchild or set BEQUEATH_DETACH=YES if PHP is "remote" from the DB server."