PHP报价问题[重复]

I have a text field called user and a submit button which displays a Json string with details of a user in the database with that id. I have the following code:

$UserID = mysql_real_escape_string($_POST['User']);

$UserCoords_Query  = "Select Accuracy, Longitude, Latitude, Timestamp 
                      FROM UserDetails
                      WHERE UserId =".$UserID;

$UserCoords_result = mysql_query($UserCoords_Query);

if (mysql_num_rows($UserCoords_result) == 0) {
    echo "There are no users with an id of ". $UserID;
}

But I am getting an error of:

Warning: mysql_num_rows() expects parameter 1 to be resource, boolean given in /home/roseanne/public_html/display_Coords.php on line 29.

I had recently switched the type of userID in my database from int to text. It worked as an int but not since the change. Can anyone see the quotes problem?

</div>

Timestamp is reserved word in mysql, use ` around it

$UserCoords_Query  = "Select `Accuracy`, `Longitude`, `Latitude`, `Timestamp`
                  FROM UserDetails
                  WHERE UserId = '".$UserID."'";

mysql_query returns false on failure, so you have to check for it. In your case it returned false - your query failed, but you still passed this false value into function mysql_num_rows, which raised an error.

Also, you should use mysqli_* as mysql_* is deprecated.

$UserID = mysql_real_escape_string($_POST['User']);

$UserCoords_Query  = "Select `Accuracy`, `Longitude`, `Latitude`, `Timestamp` 
                      FROM UserDetails
                      WHERE UserId =".$UserID;

$UserCoords_result = mysql_query($UserCoords_Query);

if ($UserCoords_result && mysql_num_rows($UserCoords_result) >= 1) {
  //Fetch results
} else {
  echo "There are no users with an id of ". $UserID;
}

$UserCoords_result is not being set as a valid resource for the function mysql_num_rows(). This may be due to mysql_query trying to run without you first creating a connection to your database. I would need to see more code to be sure.

Also while you are developing this, I would suggest you move to mysqli or DBO as mysql_ functions are being depreciated as of PHP5.5

:)