PDOStatement::$queryString "readonly" is not properly implemented

[nielsdos]

Description

The following code:

<?php
$stmt = new PDOStatement();
var_dump($stmt);
for($i=0;$i<10;$i++)
        $stmt->queryString = (string) $i;
var_dump($stmt);

Resulted in this output:

object(PDOStatement)#1 (0) {
  ["queryString"]=>
  uninitialized(string)
}
object(PDOStatement)#1 (1) {
  ["queryString"]=>
  string(1) "9"
}

But I expected this output instead:

object(PDOStatement)#1 (0) {
  ["queryString"]=>
  uninitialized(string)
}
Fatal error: Uncaught Error: Property queryString is read only in x.php:5

The reason this happens is because the following code is wrong:

php-src/ext/pdo/pdo_stmt.c

Lines 2008 to 2014 in 209e0d6

	if (zend_string_equals_literal(name, "queryString")) {
	zval *query_string = OBJ_PROP_NUM(object, 0);
	if (!Z_ISUNDEF_P(query_string)) {
	zend_throw_error(NULL, "Property queryString is read only");
	return value;
	}
	}

The second loop iteration just reuses the cache slot and won't go through the write handler, bypassing the fake readonly check.
Either this should be relaxed or be fixed (i.e. "real readonly").

PHP Version

8.3+

Operating System

No response

[nielsdos]

Ah and readonly is implicitly protected(set), so we can't actually have a "real" readonly property...

[nielsdos]

The easiest fix is probably this, but yeah not a fan:

diff --git a/ext/pdo/pdo_stmt.c b/ext/pdo/pdo_stmt.c
index bc823d8c391..90bdf18d89c 100644
--- a/ext/pdo/pdo_stmt.c
+++ b/ext/pdo/pdo_stmt.c
@@ -2011,6 +2011,7 @@ static zval *dbstmt_prop_write(zend_object *object, zend_string *name, zval *val
 			zend_throw_error(NULL, "Property queryString is read only");
 			return value;
 		}
+		cache_slot = NULL;
 	}
 	return zend_std_write_property(object, name, value, cache_slot);
 }