致命错误：调用一个成员函数调用setFetchMode（）非对象

Question

我得到这个错误在PHP上：

Fatal error: Call to a member function setFetchMode() on a non-object 

的源代码：

<?php 
$c1=103;//customer ID 
$c2=104;//customer ID 
try { 
$conn = new PDO("mysql:host=localhost;dbname=stored_procedure_examples","root",""); 
// execute the stored procedure 
$sql = 'CALL GetCredit($c1,$c2)';//passing customer ID 103 and 104 as parameter 
$q = $conn->query($sql); 
$q->setFetchMode(PDO::FETCH_ASSOC); 
} catch (PDOException $pe) { 
die("Error occurred:" . $pe->getMessage()); 
} 
?> 
<table> 
<tr> 
<th>Credit Limit</th> 
</tr> 
<?php while ($r = $q->fetch()): ?> 
<tr> 
<td><?php echo $r['creditlimit'] ?></td> 
</tr> 
<?php endwhile; ?> 
</table> 

MySQL的存储过程：

DELIMITER $$ 
CREATE PROCEDURE GetCredits(in p_cusno1 int(11),p_cusno2 int(11)) 
BEGIN 
SELECT creditlimit FROM customers WHERE customerNumber IN(p_cusno1,p_cusno2); 
END$$ 

注意：如果我直接传递客户ID，它会起作用

如果我通过间接使用变量，如c1和c2它抛出错误

Fatal error: Call to a member function setFetchMode() on a non-object 

Answer 1

通过双引号传递的变量，因为单引号没有得到变量的值。

change: 
$sql = 'CALL GetCredit($c1,$c2)'; 

to: 
$sql = "CALL GetCredit($c1,$c2)";