pdo_stmt_t definition

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

    /* if true, we've already successfully executed this statement at least
     * once */
    unsigned executed:1;                
    /* 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;   

    /* 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;                   
    struct pdo_column_data *columns;    

    /* 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;
};