configure: error: Oracle Instant Client SDK header files not found

Hi All,
i am having problem in configuring php with oracle client, i am trying it for last two days but couldn't make it, anyone have any better idea about it
as i have
RHEL - 5
php 5.2.6
oracle client = 10.2.0.4

when i issues ./configure command it gives me output as below (show error in last line=BOLD)

./configure prefix=/wwwroot/php with-apxs2=/wwwroot/bin/apxs with-config-file-path=/wwwroot/php with-mysql --with-oci8=instantclient,/usr/lib/oracle/10.2.0.4/client/lib
.........
..................
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checking for LDAP Cyrus SASL support... no
checking whether to enable multibyte string support... no
checking whether to enable multibyte regex support... yes
checking whether to check multibyte regex backtrack... yes
checking for external libmbfl... no
checking for mcrypt support... no
checking for mhash support... no
checking whether to include mime_magic support... no
checking for MING support... no
checking for mSQL support... no
checking for MSSQL support via FreeTDS... no
checking for MySQL support... yes
checking for specified location of the MySQL UNIX socket... no
checking for MySQL UNIX socket location... /var/lib/mysql/mysql.sock
checking for mysql_close in -lmysqlclient... (cached) yes
checking for MySQLi support... no
checking whether to enable embedded MySQLi support... no
checking for ncurses support... no
checking for Oracle (OCI8) support... yes
checking PHP version... 5.2.6, ok
checking size of long int... (cached) 4
checking Oracle Instant Client directory... /usr/lib/oracle/10.2.0.4/client/lib
checking Oracle Instant Client SDK header directory... configure: error: Oracle Instant Client SDK header files not found


i am doing it step by step as the instructions are written in oracle website, can anybody help me
any kind of help will be highly appreciated