I configured php4 with....
 ./configure --with-apache=../apache_1.3.11 \
--with-ldap=../openldap-1.2.10 \
--with-imap=../imap-4.7a \
--with-mysql \
--with-gd \
--enable-track-vars 

I tried the following script....
<?php
echo "Connecting Ldap...";
$ds=ldap_connect("127.0.0.1");  

if ($ds) { 
    echo "connect result is ".$ds."\n";
} else {
    echo "Unable to connect to LDAP server";
}
?>

and get "Connecting Ldap...Unable to connect to LDAP server"

I've also tried linking to openLDAP 1.2.9... same thing. It worked fine under php3.0.14. Many people on the IMP mailing list are having the same problems. I've also run tcpdump and the query never hits the network. I'm at a loss.