test1.php- <?php
$connection = ldap_connect('ldaps://local.slapd', 636);
ldap_set_option($connection, LDAP_OPT_PROTOCOL_VERSION, 3);
ldap_set_option($connection, LDAP_OPT_X_TLS_CACERTFILE, '/path/to/cacert.pem');
ldap_set_option($connection, LDAP_OPT_X_TLS_CERTFILE, '/path/to/clientcert.pem');
ldap_set_option($connection, LDAP_OPT_X_TLS_KEYFILE, '/path/to/clientkey.pem');

@ldap_bind($connection, 'avaliddn', 'password');
ldap_get_option($connection, LDAP_OPT_DIAGNOSTIC_MESSAGE, $error);
var_dump($error);

test2.php- <?php
$connection = ldap_connect('ldaps://local.slapd2', 636);
ldap_set_option($connection, LDAP_OPT_PROTOCOL_VERSION, 3);
ldap_set_option($connection, LDAP_OPT_X_TLS_CACERTFILE, '/path/to/cacert2.pem');
ldap_set_option($connection, LDAP_OPT_X_TLS_CERTFILE, '/path/to/clientcert2.pem');
ldap_set_option($connection, LDAP_OPT_X_TLS_KEYFILE, '/path/to/clientkey2.pem');

@ldap_bind($connection, 'avaliddn', 'password');
ldap_get_option($connection, LDAP_OPT_DIAGNOSTIC_MESSAGE, $error);
var_dump($error);