PHP 7.1 added support for configuring the LDAP CA/Cert environment directly, rather than relying on the environment variables. I noticed that a lot of people are having trouble getting this to work.
The correct way is:
$ds=ldap_connect("ldap.google.com");
ldap_set_option(NULL, LDAP_OPT_X_TLS_CERTFILE, "/path/file.crt");
ldap_set_option(NULL, LDAP_OPT_X_TLS_KEYFILE, "/path/file.key");
ldap_set_option($ds, LDAP_OPT_PROTOCOL_VERSION, 3);
ldap_set_option($ds, LDAP_OPT_REFERRALS, 0);
ldap_start_tls($ds);
...
ldap_close($ds);
