问题
I've just changed a site over to a new server, and now I'm getting an error with this code:
<?php
$result = mysql_query("SELECT * FROM trends ");
$num_rows = mysql_num_rows($result);
echo "<strong>" . $num_rows . "</strong>";
?>
The error is:
Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given.
How can I fix this?
Cheers.
回答1:
Your mysql_query return false if it fails.
"For SELECT, SHOW, DESCRIBE, EXPLAIN and other statements returning resultset, mysql_query() returns a resource on success, or FALSE on error." (http://php.net/manual/en/function.mysql-query.php)
Therefore you need to check if the query failed (which is the case here) before using the result.
来源：https://stackoverflow.com/questions/26476056/warning-mysql-num-rows-expects-parameter-1-to-be-resource-boolean-given