Sorry, meant to post my configure line also...
CFLAGS="-DSYB_LP64" ./configure  --prefix=${TDIR}/php-5.3.0 --with-ldap --enable-libgcc --with-oci8 --with-pdo-oci --with-sybase-ct=${SYBASE}/${SYBASE_OCS} --with-pdo-dblib=${TDIR}/freetds-0.82 --with-curl --enable-pcntl --with-gettext --with-mcrypt --enable-soap --with-pear --with-zlib --disable-cgi --with-readline --with-bz2 --with-apxs2=${TDIR}/httpd-2.2.13/bin/apxs --with-libxml-dir=${TDIR}/libxml2-2.7.5 --with-xsl=${TDIR}/libxslt-1.1.26 --with-openssl=${TDIR}/openssl-0.9.8k

Your configure line is missing this: --with-libdir=lib64

Firstly, many thanks for picking this up.
-
The rest of my PHP configuration relies on libs in /usr/lib64 and that works. I didn't use --with-libdir=lib64 because my LD_LIBRARY_PATH and SHLIB_PATH include /usr/lib64 and are set to:

/opt/sybase/Connect64forODBC60/lib:/opt/sybase/httpd-2.2.13/lib:/opt/sybase/libxslt-1.1.26/lib:/opt/sybase/libxml2-2.7.5/lib:/opt/sybase/freetds-0.82/lib:/opt/sybase/openssl-0.9.8k/lib:/opt/sybase/DBA_SDK1500-16721/DataAccess/ODBC/lib:/opt/sybase/DBA_SDK1500-16721/OCS-15_0/lib:/opt/sybase/DBA_SDK1500-16721/OCS-15_0/lib3p:/usr/lib64:/lib64:/usr/X11R6/lib64:/opt/gnome/lib64:/usr/local/lib64:/usr/X11R6/lib/X11/locale/lib64:/usr/X11R6/lib64:/var/lib/stunnel/lib64:/u01/sq/ora_1/oracle/client/11.2.0/lib:/usr/lib64:/usr/lib:/home/db2inst/sqllib/lib64:/home/db2inst/sqllib/lib32

The problem with setting --with-libdir=lib64 is that not all software that I'm linking against has libs in lib64, some are just in lib.

Okay, found all the software where only lib exists and created a suitable link to lib from lib64. Specifiying the --with-libdir=lib64, now means that it compiles with the --with-ldap. Thanks for the help.

useful howto
http://wiki.lepr-e.com/wiki/index.php/Ubuntu_Smtp_Server

I would like to bring this up again, considering to re-open this ticket. The LDAP extension seems to be the only extension that does *not* find the header file and libraries on 64bit distros by default, i.e. without explicitly specifying the library path. This is still true for all 5.3 versions and even 5.4.0RC1.

Nevermind, looks like libldap seems to be the only library used for building PHP that installs into /usr/lib/x86_64-linux-gnu and does *not* provide a ldap-config script or similar to determine the actual library path, like libcurl does for example.

I have to same bug with compile --with-ldap on Debian x64. LDAP libraries resides in /urs/lib/x86_64-linux-gnu . I don't want to use --with-libdir, as it breaks other paths to libs for other packages, ie --with-mysql=/opt/mysql, --with-opensll=/opt/openssl

The cnfigure script must be updated to handle this path for LDAP.
For meantime a workaround:

git checkout master;
./buildconf --force;
sed -i -e 's~^\([[:space:]]*\)\(if test -f \$LDAP_LIBDIR/liblber\.a || test -f \$LDAP_LIBDIR/liblber\.\$SHLIB_SUFFIX_NAME; then\)$~\1if test -f \$LDAP_LIBDIR/x86_64-linux-gnu/liblber\.a || test -f \$LDAP_LIBDIR/x86_64-linux-gnu/liblber\.\$SHLIB_SUFFIX_NAME; then\n\1  LDAP_LIBDIR=$LDAP_LIBDIR/x86_64-linux-gnu\n\1fi\n\n\1\2~' configure;
./configure --prefix=/opt/php --with-ldap

注意：开始我用--with-ldap安装编译的时候一直报错
configure: error: Cannot find ldap libraries in /usr/lib. 或者configure: error: Cannot find ldap.h
而经过检查openldap-devel都是安装的，当时因为一直没解决我就先放弃了ldap.
后面想还是尝试一下ldap扩展，于是源包目录,安装过程是成功的。
cd /opt/soft/php-5.6.8/ext/ldap
  /data/php/bin/phpize
 ./configure  --with-php-config=/data/php/bin/php-config  --with-ldap  --with-libdir=lib64 
主要是--with-libdir=lib64

I found this useful, see last comment to solve issue of:

configure: error: Cannot find ldap.h
-

Anyone want to try my PR at https://github.com/php/php-src/pull/2754 ?