Solaris 2.7 on Ultra5, gcc2.8.8, apache1.3.9, OpenLDAP
Using php4b2:
configure --with-apache=../apache139 --with-ldap=/usr --enable-track-vars --enable-force-cgi-redirect

make results:
Making all in libzend
Making all in ext
Making all in apache
Making all in db
Making all in ldap
gcc -DHAVE_CONFIG_H -I. -I. -I../.. -I../../libzend -I../../TSRM -I/usr/share/src/php4b2/../apache139/src/include -I/usr/share/src/php4b2/../apache139/src/os/unix  -I/usr/include   -I../.. -I../../libzend    -g -O2 -g -O2 -c ldap.c
ldap.c:70: `php3_ldap_close' undeclared here (not in a function)
ldap.c:70: initializer element for `ldap_functions[1].handler' is not constant
ldap.c: In function `php3_ldap_bind':
ldap.c:506: dereferencing pointer to incomplete type
ldap.c: In function `php3_ldap_do_search':
ldap.c:623: dereferencing pointer to incomplete type
ldap.c: In function `php3_ldap_get_values':
ldap.c:1003: dereferencing pointer to incomplete type
*** Error code 1
make: Fatal error: Command failed for target `ldap.o'
Current working directory /usr/share/src/php4b2/ext/ldap
*** Error code 1
make: Fatal error: Command failed for target `all-recursive'
Current working directory /usr/share/src/php4b2/ext
*** Error code 1
make: Fatal error: Command failed for target `all-recursive'
++++++++++++++++++++++++++++++++++++++++++++++++++

Using php3.0.12 with same configure.
make results:
gcc -g -O2 -O2   -I. -I.   -I../apache139/src/include -I../apache139/src/os/unix                  -I/usr/include    -c language-parser.tab.c -o language-parser.tab.o
gcc -g -O2 -O2   -I. -I.   -I../apache139/src/include -I../apache139/src/os/unix                  -I/usr/include    -w -DYY_USE_CONST -c language-scanner.c
gcc -g -O2 -O2   -I. -I.   -I../apache139/src/include -I../apache139/src/os/unix                  -I/usr/include    -c main.c -o main.o
main.c: In function `php3_printf':
main.c:308: `__builtin_va_alist' undeclared (first use in this function)
main.c:308: (Each undeclared identifier is reported only once
main.c:308: for each function it appears in.)
main.c: In function `php3_error':
main.c:381: `__builtin_va_alist' undeclared (first use in this function)
*** Error code 1
make: Fatal error: Command failed for target `main.o'

Ditch the '--with-ldap' and it compiles fine.