php - Trying to understand function query in zend -

/**      * prepares , executes sql statement bound data.      *      * @param  mixed  $sql  sql statement placeholders.      *                      may string or zend_db_select.      * @param  mixed  $bind array of data bind placeholders.      * @return zend_db_statement_interface      */      public function query($sql, $bind = array())         {             // connect database if needed             $this->_connect();              // $sql zend_db_select object?             if ($sql instanceof zend_db_select) {                 if (empty($bind)) {                     $bind = $sql->getbind();                 }                  $sql = $sql->assemble();             }              // make sure $bind array;             // don't use (array) typecasting because             // because $bind may zend_db_expr object             if (!is_array($bind)) {                 $bind = array($bind);             }              // prepare , execute statement profiling             $stmt = $this->prepare($sql);             $stmt->execute($bind);              // return results embedded in prepared statement object             $stmt->setfetchmode($this->_fetchmode);             return $stmt;         } 

above code zend/db/adapter/abstract.php, although there comment, still not understand usage of $bind. if possible, please explain example.
thanks.

$bind array argument parametrized queries:

// $bind single param: $obj->query('select * tablename idcolumn = ?', array(1)); // or $obj->query('select * tablename idcolumn = ?', 1); 

means:

select * tablename idcolumn = 1 

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// $bind multiparams: $obj->query('select * tablename somefield between ? , ?', array(10, 15)); 

means:

select * tablename somefield between 10 , 15 

---

// $bind omitted @ all: $obj->query('select * tablename order somefield'); 

means:

select * tablename order somefield 

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if $sql instance of zend_db_select, may have own bindings. if supplied $bind empty / omitted, $sql's binding assigned it.