4

This query returns 5 results in phpMyAdmin:

SELECT * FROM tbl_product WHERE 1 ORDER BY last_update DESC LIMIT 0,5

And this returns count=12 in phpMyAdmin (which is fine, because there are 12 records):

SELECT COUNT(*) AS count FROM tbl_product WHERE 1 ORDER BY last_update DESC LIMIT 0,5

This function was working fine before I added the two variables (offset, display), however now it doesn't work, and printing the variables out gives me offset=0, display=5 (so still LIMIT 0,5).

function getProducts($offset, $display) {
    $sql = "SELECT * FROM tbl_product WHERE 1 ORDER BY last_update DESC LIMIT ?,?;";
    $data = array((int)$offset, (int)$display);
    $rows = dbRowsCount($sql, $data);
logErrors("getProducts(".$offset.",".$display.") returned ".$rows." rows.");
    if ($rows > 0) {
        dbQuery($sql, $data);
        return dbFetchAll();
    } else {
        return null;
    }
}

It's not working because my dbRowsCount(...) method was returning empty string (stupid PDOStatement::fetchColumn), so I changed it to return the count with PDO::FETCH_ASSOC and it returns count=0.

Here is the function which does the row-count:

function dbRowsCount($sql, $data) {
    global $db, $query;
    $regex = '/^SELECT\s+(?:ALL\s+|DISTINCT\s+)?(?:.*?)\s+FROM\s+(.*)$/is';
    if (preg_match($regex, $sql, $output) > 0) {
        $query = $db->prepare("SELECT COUNT(*) AS count FROM {$output[1]}");
logErrors("Regex output: "."SELECT COUNT(*) AS count FROM {$output[1]}");
        $query->setFetchMode(PDO::FETCH_ASSOC);
        if ($data != null) $query->execute($data); else $query->execute();
        if (!$query) {
            echo "Oops! There was an error: PDOStatement returned false.";
            exit;
        }
        $result = $query->fetch();
        return (int)$result["count"];
    } else {
logErrors("Regex did not match: ".$sql);
    }
    return -1;
}

My error log gives me this output from the program:

Regex output: SELECT COUNT(*) AS count FROM tbl_product WHERE 1 ORDER BY last_update DESC LIMIT ?,?;
getProducts(0,5) returned 0 rows.

As you can see, the SQL has not been malformed, and the method input variables were 0 and 5 as expected.

Does anyone know what has gone wrong?

Update

Following a suggestion, I did try to execute the query directly, and it returned the correct result:

function dbDebugTest() {
    global $db;
    $stmt = $db->query("SELECT COUNT(*) AS count FROM tbl_product WHERE 1 ORDER BY last_update LIMIT 0,5;");
    $result = $stmt->fetch();
    $rows = (int)$result["count"];
    logErrors("dbDebugTest() returned rows=".$rows);
}

Output:

> dbDebugTest() returned rows=12

Following another suggestion, I changed !=null to !==null, and I also printed out the $data array:

logErrors("Data: ".implode(",",$data));
if ($data !== null) $query->execute($data); else $query->execute();

Output:

> Data: 0,5

However, the dbRowsCount($sql, $data) still returns 0 rows for this query!

Update 2

Following advice to implement a custom PDOStatement class which would allow me to output the query after the values have been binded, I found that the function would stop after $query->execute($data) and so the output would not be printed, although the custom class works for every other query in my program.

Updated code:

function dbRowsCount($sql, $data) {
    global $db, $query;
    $regex = '/^SELECT\s+(?:ALL\s+|DISTINCT\s+)?(?:.*?)\s+FROM\s+(.*)$/is';
    if (preg_match($regex, $sql, $output) > 0) {
        $query = $db->prepare("SELECT COUNT(*) AS count FROM {$output[1]}");
logErrors("Regex output: "."SELECT COUNT(*) AS count FROM {$output[1]}");
        $query->setFetchMode(PDO::FETCH_ASSOC);
logErrors("Data: ".implode(",",$data));
        $query->execute($data);
logErrors("queryString:".$query->queryString);
logErrors("_debugQuery():".$query->_debugQuery());
        if (!$query) {
            echo "Oops! There was an error: PDOStatement returned false.";
            exit;
        }
        $result = $query->fetch();
        return (int)$result["count"];
    } else {
logErrors("Regex did not match: ".$sql);
    }
    return -1;
}

Output:

Regex output: SELECT COUNT() AS count FROM tbl_product_category WHERE id=?;
Data: 5
queryString:SELECT COUNT() AS count FROM tbl_product_category WHERE id=?;
_debugQuery():SELECT COUNT(*) AS count FROM tbl_product_category WHERE id=?;

Regex output: SELECT COUNT(*) AS count FROM tbl_product WHERE 1 ORDER BY last_update DESC LIMIT ?,?;
Data: 0,5
// function stopped and _debugQuery couldn't be output

Update 3

Since I couldn't get the custom PDOStatement class to give me some output, I thought I'd rewrite the getProducts(...) class to bind the params with named placeholders instead.

function getProducts($offset, $display) {
    $sql = "SELECT * FROM tbl_product WHERE 1 ORDER BY last_update DESC LIMIT :offset, :display;";
    $data = array(':offset'=>$offset, ':display'=>$display);
    $rows = dbRowsCount($sql, $data);
logErrors("getProducts(".$offset.",".$display.") returned ".$rows." rows.");
    if ($rows > 0) {
        dbQuery($sql, $data);
        return dbFetchAll();
    } else {
        return null;
    }
}

Output:

Regex output: SELECT COUNT(*) AS count FROM tbl_product WHERE 1 ORDER BY last_update DESC LIMIT :offset, :display;
Data: 0,5
// Still crashes after $query->execute($data) and so logErrors("getProducts(".$offset."...)) wasn't printed out

Update 4

This dbDebugTest previously worked with declaring the limit values 0,5 directly in the SQL string. Now I've updated it to bind the parameters properly:

function dbDebugTest($offset, $display) {
    logErrors("Beginning dbDebugTest()");
    global $db;
    $stmt = $db->prepare("SELECT COUNT(*) AS count FROM tbl_product WHERE 1 ORDER BY last_update LIMIT :offset,:display;");
    $stmt->bindParam(':offset', $offset, PDO::PARAM_INT);
    $stmt->bindParam(':display', $display, PDO::PARAM_INT);
    if ($stmt->execute()) {
      $result = $stmt->fetch();
      $rows = (int)$result["count"];
      logErrors("dbDebugTest() returned rows=".$rows);
    } else {
      logErrors("dbDebugTest() failed!");
    }
}

The function crashes, and only this is output:

Beginning dbDebugTest()

Update 5

Following a suggestion to turn errors on (they are off by default), I did this:

$db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

That itself, made the dbDebugTest() from Update 4 work!

Beginning dbDebugTest() dbDebugTest() returned rows=12

And now an error is generated in my webserver logs:

[warn] mod_fcgid: stderr: PHP Fatal error:
Uncaught exception 'PDOException' with message 'SQLSTATE[42000]:
Syntax error or access violation: 1064 You have an error in your SQL syntax;
check the manual that corresponds to your MySQL server version for the right syntax to use
near ''0', '5'' at line 1'
in /home/linweb09/b/example.com-1050548206/user/my_program/database/dal.php:36

Line 36 refers to dbRowsCount(...) method and the line is $query->execute($data).

So the other method getProducts(...) still doesn't work because it uses this method of binding the data and the params turn into ''0' and '5'' (is this a bug?). A bit annoying but I'll have to create a new method in my dal.php to allow myself to bind the params in the stricter way - with bindParam.

Thanks especially to @Travesty3 and @eggyal for their help!! Much, much appreciated.

4

2 回答 2

2

根据问题中的更新 2，在execute语句之后执行停止，看起来查询失败了。查看一些 PDO 文档后，默认错误处理设置似乎是 PDO::ERRMODE_SILENT，这将导致您看到的行为。

这很可能是由于您的 LIMIT 子句中的数字在作为参数传入时被放入单引号中，就像在这篇文章中发生的那样。

该帖子的解决方案是使用该bindValue方法将参数指定为整数。所以你可能不得不做类似的事情。

看起来您还应该使用 try-catch 块执行查询以捕获 MySQL 错误。

绑定值方法：

if ($data !== null)
{
    for ($i=0; $i<count($data); $i++)
        $query->bindValue($i+1, $data[$i], PDO::PARAM_INT);
    $query->execute($data);
}
else
    $query->execute();
于 2012-05-01T18:44:45.320 回答
1

您正在测试是否$data使用NULL相等运算符而不是标识运算符（有关各种比较运算符如何处理值的更多信息，请参阅PHP 手册）。NULL您需要使用身份测试===/ !==，或者调用is_null().

正如上面提到的@Travesty3，要测试数组是否为空，请使用empty().

于 2012-05-01T17:25:13.263 回答