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pdo_stmt_t definition

All fields should be treated as read-only unless explicitly stated otherwise.

Figure 45-2. pdo_stmt_t

/* represents a prepared statement */
struct _pdo_stmt_t {
    /* driver specifics */
    struct pdo_stmt_methods *methods;   (1)
    void *driver_data;                  (2)

    /* if true, we've already successfully executed this statement at least
     * once */
    unsigned executed:1;                (3)
    /* if true, the statement supports placeholders and can implement
     * bindParam() for its prepared statements, if false, PDO should
     * emulate prepare and bind on its behalf */
    unsigned supports_placeholders:2;   (4)

    /* the number of columns in the result set; not valid until after
     * the statement has been executed at least once.  In some cases, might
     * not be valid until fetch (at the driver level) has been called at least once.
     * */
    int column_count;                   (5)
    struct pdo_column_data *columns;    (6)

    /* points at the dbh that this statement was prepared on */
    pdo_dbh_t *dbh;

    /* keep track of bound input parameters.  Some drivers support
     * input/output parameters, but you can't rely on that working */
    HashTable *bound_params;
    /* When rewriting from named to positional, this maps positions to names */
    HashTable *bound_param_map; 
    /* keep track of PHP variables bound to named (or positional) columns
     * in the result set */
    HashTable *bound_columns;

    /* not always meaningful */
    long row_count;

    /* used to hold the statement's current query */
    char *query_string;
    int query_stringlen;

    /* the copy of the query with expanded binds ONLY for emulated-prepare drivers */
    char *active_query_string;
    int active_query_stringlen;

    /* the cursor specific error code. */
    pdo_error_type error_code;

    /* used by the query parser for driver specific
     * parameter naming (see pgsql driver for example) */
    const char *named_rewrite_template;
};
(1)
The driver must set this during SKEL_handle_preparer().
(2)
This item is for use by the driver; the intended usage is to store a pointer (during SKEL_handle_factory()) to whatever instance data is required to maintain a connection to the database.
(3)
This is set by PDO after the statement has been executed for the first time. Your driver can inspect this value to determine if it can skip one-time actions as an optimization.
(4)
Discussed in more detail in the Section called SKEL_handle_preparer
(5)
Your driver is responsible for setting this field to the number of columns available in a result set. This is usually set during SKEL_stmt_execute() but with some database implementations, the column count may not be available until SKEL_stmt_fetch() has been called at least once. Drivers that SKEL_stmt_next_rowset() should update the column count when a new rowset is available.
(6)
PDO will allocate this field based on the value that you set for the column count. You are responsible for populating each column during SKEL_stmt_describe(). You must set the precision, maxlen, name, namelen and param_type members for each column. The name is expected to be allocated using emalloc(); PDO will efree() at the appropriate time.
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