php mysql_error() 不显示错误
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mysql_error() not displaying an error
提问by nitrous
I am trying to debug my code but mysql_error() isn't displaying anything. I know there is something wrong, because when I write
我正在尝试调试我的代码，但 mysql_error() 没有显示任何内容。我知道有问题，因为当我写
or die("ERROR");
It displays ERROR. So the problem must be with that line of code. When I write
它显示错误。所以问题一定出在这行代码上。当我写
or die(mysql_error());
It shows up blank. Here is my code for the line that I think has the error:
它显示为空白。这是我认为有错误的行的代码：
while ($rows = mysql_fetch_array($sql6) or die(mysql_error())) {
Now here is the full code block:
现在这里是完整的代码块：
$sql6 = mysql_query("SELECT * FROM replies WHERE thread_id = $thread_id");
$numRows = mysql_num_rows($sql6);
$replies = '';
if ($numRows < 1) {
$replies = "There are no replies yet, you can make the first!";
} else {
while ($rows = mysql_fetch_array($sql6) or die(mysql_error())) {
$reply_content = $rows['5'];
$reply_username = $rows['7'];
$reply_date = $rows['8'];
$reply_author_id = $rows['4'];
$sql9 = mysql_query("SELECT * FROM users WHERE id = '$reply_author_id'");
$numRows = mysql_num_rows($sql9);
if ($numRows < 1) {
while ($rows = mysql_fetch_array($sql9)) {
$reply_user_fn = $rows['first_name'];
$reply_user_ln = $rows['last_name'];
$reply_user_id = $rows['id'];
$reply_user_pp = $rows['profile_pic'];
$reply_user_lvl = $rows['user_level'];
$reply_user_threads = $rows['threads'];
$reply_user_email = $rows['email'];
$replies .= '<tr><td valign="top" style="border: 1px solid black;">';
$replies .= '<div class="reply" style="min-height: 125px;"';
$replies .= '<h2>Re: ' . $thread_title . '</h2><br />';
$replies .= '<em>by: ' . $reply_username . ' - ' . $reply_date . '</em><hr />';
$replies .= $reply_content;
$replies .= '</div></td>';
$replies .= '<td valign="top" width="200" align="center" style="border: 1px solid black;"';
$replies .= '<img src="userdata/profile_pics/' . $reply_user_pp . '" width="80" height="80"><br />';
$replies .= '<a href="profile.php?u=' .$reply_username . '" style="color: black;">'. $reply_username .'</a><br />';
$replies .= '<a href="profile.php?u=' .$reply_username . '" style="color: black;">' . $reply_user_fn.' ' .$reply_user_ln . '</a><br />';
$replies .= 'Threads: ' . $reply_user_threads . ' <br />Level: '. $reply_user_lvl .'<br />Sign up date: ' . $reply_user_email/*PUT SIGNUP DATE*/ .'';
$replies .= '<input type="button" name="addfriend" value="Add Friend">';
$replies .= '</td>';
}
}
}
}
What am I doing wrong and why won't PHP display the mysql error? Thanks
我做错了什么，为什么 PHP 不显示 mysql 错误？谢谢
回答by Sammitch
Do not put or die()inside of a loop condition. The loop condition becoming falseis what signals the loop to end, and that will also trigger die()every time your loop completes.
不要放在or die()循环条件内。循环条件变成false是循环结束的信号，并且die()每次循环完成时也会触发。
mysql_fetch_row()returns false when there are no more rows this is what is triggering your die()statement despite there being no error.
mysql_fetch_row()当没有更多行时返回false，die()尽管没有错误，但这是触发您的语句的原因。
回答by Stoic
You can use a try..catchblock to understand why your code is not working correctly, like this:
您可以使用try..catch块来了解您的代码为何无法正常工作，如下所示：
try {
while ($rows = mysql_fetch_array($sql6)) {
// your code ..
}
} catch (Exception $e) {
echo $e->getMessage();
echo "---";
echo mysql_error();
}
Note that, as you say or dieis getting executed, which means that there is an error in your code somewhere, and not a mysql error. And, therefore, the above code will capture that exception and display it for you. Also, it will display any mysql_error, if it has occurred until that point for reference, so that you can compare the two strings.
请注意，正如您所说or die的正在执行，这意味着您的代码中某处存在错误，而不是mysql error. 因此，上面的代码将捕获该异常并为您显示。此外，它会显示 any mysql_error，如果它在该点之前发生过以供参考，以便您可以比较两个字符串。
回答by Alejandro Iván
There is no mysql_error()because mysql_query()is probably correct.
没有mysql_error()因为mysql_query()可能是正确的。
You do mysql_error()immediately afterthe query, because it will show a message if the querywas wrong, not the PHP code that gets the rows.
您在查询mysql_error()后立即执行，因为如果查询错误，它将显示一条消息，而不是获取行的 PHP 代码。
$conn = mysql_connect(....);
$sql6 = mysql_query("...", $conn) or die(mysql_error($conn));
// ...
while ($rows = mysql_fetch_array()) { ... } // There's no mysql_error() here, it will return a data set (or not enter the while code block if it's null9
回答by DecoderNT
If still no mysql error, after changing the "or die" position after "mysql_query"..do you get $thread_id from somewhere?? like
如果仍然没有 mysql 错误，在“mysql_query”之后更改“or die”位置后..你从某个地方得到 $thread_id 吗？喜欢
$thread_id=$_GET['thread_id'];
Also, if you use, multiple database connections, inside mysql_error('$connection_name'))
此外，如果您使用多个数据库连接，在 mysql_error('$connection_name')) 中
Like:
喜欢：
//Connect to database
$main = mysql_connect(DB_HST, DB_USR, DB_PSS);
mysql_select_db(DB_DB);
$main2 = mysql_connect(DB_HST2, DB_USR2, DB_PSS2);
mysql_select_db(DB_DB2);
return the error executing the query to the right database..
将执行查询的错误返回到正确的数据库..
mysql_query("query") or die (mysql_error($main));
when using multiple database connection the query should look like:
使用多个数据库连接时，查询应如下所示：
$query = mysql_query("SELECT * FROM table_name WHERE id=1", $connection_name);
mysql_fetch_array($query);
回答by user3092162
I had similar problem of not seeing any error messages from mysql. After research it appeared that the problem has got nothing to do with PHP itself, but with mysql server configuration. The default value of the variable lc_messages_dirpointed to non existing directory. After adding a line in mysqld.cnf, then restarted the mysql server, and finally it worked. For me the following was the right one:
我有类似的问题，没有看到来自 mysql 的任何错误消息。经过研究，问题似乎与 PHP 本身无关，而与 mysql 服务器配置有关。变量lc_messages_dir的默认值指向不存在的目录。在mysqld.cnf中添加一行后，然后重启mysql服务器，终于成功了。对我来说，以下是正确的：
lc_messages_dir=/usr/share/mysql
It is described in mysql reference manual: https://dev.mysql.com/doc/refman/5.7/en/error-message-language.html
它在mysql参考手册中有描述：https: //dev.mysql.com/doc/refman/5.7/en/error-message-language.html
