(PHP 5 >= 5.3.0, PHP 7, PHP 8)
SQLite3Stmt::clear — Clears all current bound parameters
   Clears all current bound parameters (sets them to null).
  
    This method needs to be used with SQLite3Stmt::reset().
    If used alone, any call to 
    SQLite3Stmt::bindValue() or
    SQLite3Stmt::bindParam() will be of no effect
    and all bound parameters will have the null value.
   
此函数没有参数。
   Returns true on successful clearing of bound parameters, false on
   failure.