If you want to disable the TLS cert check (e.g. because you are doing an SSH port-forward, and ldaps is pointing to localhost), then you must invoke:
ldap_set_option(NULL, LDAP_OPT_X_TLS_REQUIRE_CERT,0)
*before* calling ldap_connect()
If you try:
$ds = ldap_connect(...)
ldap_set_option($ds, LDAP_OPT_X_TLS_REQUIRE_CERT,0)
then the option won't actually take effect, and the certificate will be checked anyway, and a TLS failure will happen..