[pdo_firebird] Added pdo_firebird_check_liveness

UPGRADING

@@ -223,6 +223,8 @@ PHP 8.4 UPGRADE NOTES
     Along with these, five constants (PDO::FB_TRANSACTION_ISOLATION_LEVEL,
     PDO::FB_READ_COMMITTED, PDO::FB_REPEATABLE_READ, PDO::FB_SERIALIZABLE,
     PDO::FB_WRITABLE_TRANSACTION) have been added.
+  . When using persistent connections, there is now a liveness check in the
+    constructor.
 
 - PDO_MYSQL:
   . getAttribute, enabled to get the value of ATTR_FETCH_TABLE_NAMES.

ext/pdo_firebird/firebird_driver.c

@@ -1216,6 +1216,18 @@ static int pdo_firebird_get_attribute(pdo_dbh_t *dbh, zend_long attr, zval *val)
 }
 /* }}} */
 
+#if FB_API_VER >= 30
+/* called by PDO to check liveness */
+static zend_result pdo_firebird_check_liveness(pdo_dbh_t *dbh) /* {{{ */
+{
+	pdo_firebird_db_handle *H = (pdo_firebird_db_handle *)dbh->driver_data;
+
+	/* fb_ping return 0 if the connection is alive */
+	return fb_ping(H->isc_status, &H->db) ? FAILURE : SUCCESS;
+}
+/* }}} */
+#endif
+
 /* called by PDO to retrieve driver-specific information about an error that has occurred */
 static void pdo_firebird_fetch_error_func(pdo_dbh_t *dbh, pdo_stmt_t *stmt, zval *info) /* {{{ */
 {
@@ -1254,7 +1266,11 @@ static const struct pdo_dbh_methods firebird_methods = { /* {{{ */
 	NULL, /* last_id not supported */
 	pdo_firebird_fetch_error_func,
 	pdo_firebird_get_attribute,
-	NULL, /* check_liveness */
+#if FB_API_VER >= 30
+	pdo_firebird_check_liveness,
+#else
+	NULL,
+#endif
 	NULL, /* get driver methods */
 	NULL, /* request shutdown */
 	pdo_firebird_in_manually_transaction,

ext/pdo_firebird/tests/persistent_connect.phpt

@@ -0,0 +1,47 @@
+--TEST--
+PDO_Firebird: persistent connect test
+--EXTENSIONS--
+pdo_firebird
+--SKIPIF--
+<?php require('skipif.inc'); ?>
+--XLEAK--
+A bug in firebird causes a memory leak when calling `isc_attach_database()`.
+See https://github.com/FirebirdSQL/firebird/issues/7849
+--FILE--
+<?php
+
+/**
+ * Omit the case where the connection is broken when it checks liveness and
+ * it has to reconnect, as it is very difficult to reproduce the situation.
+ */
+
+require("testdb.inc");
+unset($dbh);
+
+$connIds = [];
+
+foreach (['First', 'Second'] as $times) {
+    $dbh = new PDO(
+        PDO_FIREBIRD_TEST_DSN,
+        PDO_FIREBIRD_TEST_USER,
+        PDO_FIREBIRD_TEST_PASS,
+        [
+            PDO::ATTR_PERSISTENT => true,
+        ],
+    );
+    $stmt = $dbh->query('SELECT CURRENT_CONNECTION FROM RDB$DATABASE');
+    $connId = $stmt->fetchColumn();
+    $connIds[] = $connId;
+    echo "{$times} connection ID: {$connId}\n";
+
+    unset($dbh);
+    unset($stmt);
+    unset($connID);
+}
+
+echo $connIds[0] === $connIds[1] ? "Same ID.\n" : "Different ID\n";
+?>
+--EXPECTF--
+First connection ID: %d
+Second connection ID: %d
+Same ID.