bind_param_inout()
$sth->bind_param_inout(index, \$value,max_length[, \%attri|type])
This function associates or binds a value in an SQL statement using a placeholder. The first argument indicates which placeholder to replace with a given value, i.e., the second argument. It must be given as a reference (a variable preceded by a backslash). The values are updated when the related row is retrieved using a fetch method. The maximum length of a value is given in the third argument. Attributes may be added or the data type may be given as a fourth argument. This function is generally used with stored procedures.