-- ~oracle/.bash_profile -------------------------
umask 022
export ORACLE_BASE=/opt/oracle
export ORACLE_HOME=$ORACLE_BASE/product/8.1.7
export ORACLE_OWNER=oracle
export ORACLE_SID=oracle
export TMPDIR=$ORACLE_BASE/tmp
export PATH=.:$ORACLE_HOME/bin:/usr/local/java/bin:$PATH
export TNS_ADMIN=$ORACLE_HOME/network/admin
export NLS_LANG=American_America.KO16KSC5601
export ORA_NLS33=$ORACLE_HOME/ocommon/nls/admin/data
export LD_LIBRARY_PATH=$ORACLE_HOME/lib:$LD_LIBRARY_PATH
export LANG=C
----------------------------------------------------

http://kr.php.net/manual/en/ref.oci8.php

runtime env :

ORACLE_HOME 
ORACLE_SID 
LD_PRELOAD 
LD_LIBRARY_PATH 
NLS_LANG 
ORA_NLS33 


If your webserver doesn't start or crashes at startup: Check that Apache is linked with the pthread library: 

# ldd /www/apache/bin/httpd 
    libpthread.so.0 => /lib/libpthread.so.0 (0x4001c000)
    libm.so.6 => /lib/libm.so.6 (0x4002f000)
    libcrypt.so.1 => /lib/libcrypt.so.1 (0x4004c000)
    libdl.so.2 => /lib/libdl.so.2 (0x4007a000)
    libc.so.6 => /lib/libc.so.6 (0x4007e000)
    /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)


# cd /usr/src/apache_1.3.xx
# make clean
# LIBS=-lpthread ./config.status        <--- notice
# make
# make install

Please note that on some systems like UnixWare it is libthread instead of libpthread. PHP and Apache have to be configured with EXTRA_LIBS=-lthread.