ext/pdo_firebird: Fixed GH-15604 Always make input parameters nullable

ext/pdo_firebird/firebird_driver.c

@@ -461,6 +461,15 @@ static int php_firebird_preprocess(const zend_string* sql, char* sql_out, HashTa
 	return 1;
 }
 
+static void set_nullable_input_params(XSQLDA* sqlda)
+{
+	unsigned int i;
+	XSQLVAR* var;
+	for (i=0, var = sqlda->sqlvar; i < sqlda->sqld; i++, var++) {
+		var->sqltype |= 1;
+	}
+}
+
 #if FB_API_VER >= 40
 /* set coercing a data type */
 static void set_coercing_output_data_types(XSQLDA* sqlda)
@@ -681,6 +690,9 @@ static bool firebird_handle_preparer(pdo_dbh_t *dbh, zend_string *sql, /* {{{ */
 			if (isc_dsql_describe_bind(H->isc_status, &s, PDO_FB_SQLDA_VERSION, S->in_sqlda)) {
 				break;
 			}
+
+			// make all parameters nullable
+			set_nullable_input_params(S->in_sqlda);
 		}
 
 		stmt->driver_data = S;

ext/pdo_firebird/tests/bug_15604.phpt

@@ -0,0 +1,78 @@
+--TEST--
+Bug #15604 It is not possible to pass a NULL value as an input parameter if the field is marked as NOT NULL.
+--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
+require_once 'testdb.inc';
+
+$dbh = getDbConnection();
+
+$dbh->exec('
+recreate table t_bug_15604 (
+  id bigint not null,
+  a int not null,
+  b int,
+  constraint pk_bug_15604 primary key(id)
+)
+');
+
+$dbh->exec('recreate sequence g_bug_15604');
+
+$dbh->exec(<<<'SQL'
+create or alter trigger t_bug_15604_bi0 for t_bug_15604
+active before insert position 0
+as
+begin
+  if (new.id is null) then
+    new.id = next value for g_bug_15604;
+end
+SQL
+);
+
+$stmt = $dbh->prepare('insert into t_bug_15604(id, a, b) values(?, ?, ?)');
+$stmt->execute([null, 1, 2]);
+$stmt->execute([2, 2, null]);
+unset($stmt);
+
+$stmt2 = $dbh->prepare('SELECT id, a, b FROM t_bug_15604 WHERE id = ?');
+
+$stmt2->execute([null]); 
+$data = $stmt2->fetch(\PDO::FETCH_ASSOC);
+$stmt2->closeCursor();
+var_dump($data);
+
+$stmt2->execute([2]); 
+$data = $stmt2->fetch(\PDO::FETCH_ASSOC);
+$stmt2->closeCursor();
+var_dump($data);
+
+unset($stmt2);
+
+echo "\nOK\n";
+?>
+--EXPECT--
+bool(false)
+array(3) {
+  ["ID"]=>
+  int(2)
+  ["A"]=>
+  int(2)
+  ["B"]=>
+  NULL
+}
+
+OK
+--CLEAN--
+<?php
+require_once 'testdb.inc';
+$dbh = getDbConnection();
+@$dbh->exec('drop table t_bug_15604');
+@$dbh->exec('drop sequence g_bug_15604');
+unset($dbh);
+?>