从PDOStatement获取PDO

Question

请考虑以下几点：

$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PDOStatement的每个实例都存储一个用来创建它的DB句柄(引用lxr for PHP5.6)：

/* 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;

..。它不是通过公开的方法暴露的。

值得注意的是，pdo_dbh_t实例可以(至少看起来是这样)存储对pdo_stmt_t (链接)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;