从PDOStatement获取PDO

Question

请考虑以下事项：

$PDOStatement = $PDO->prepare($query);

是否可以从$PDO实例中获取$PDOStatement实例？

Answer 1

目前，这是不可能的。即使每个PDOStatement实例都存储了用于创建它的数据库句柄（quoting lxr for PHP 5.6）：

/* represents a prepared statement */
543 struct _pdo_stmt_t {
544    /* these items must appear in this order at the beginning of the
545       struct so that this can be cast as a zend_object.  we need this
546       to allow the extending class to escape all the custom handlers
547       that PDO declares.
548    */
549    zend_object std;
550
...
572    /* we want to keep the dbh alive while we live, so we own a reference */
573    zval database_object_handle;
574    pdo_dbh_t *dbh;

......它没有通过公共方法曝光。

---

值得注意的是，pdo_dbh_t个实例可能（至少看起来如此）存储对pdo_stmt_t（link）的引用：

427 /* represents a connection to a database */
428 struct _pdo_dbh_t {
... 
501    /* when calling PDO::query(), we need to keep the error
502     * context from the statement around until we next clear it.
503     * This will allow us to report the correct error message
504     * when PDO::query() fails */
505    pdo_stmt_t *query_stmt;