php array num_rows无法正常工作

Question

I was wondering if my array had been done correctly. Here is the code:

  $sql = "SELECT * FROM user WHERE user_id = '".$user_id."' ORDER BY user_id DESC";
  $numRowsSet = array();
  while($numRows = mysql_num_rows($sql)){
   $numRowsSet[] = $numRows;
  }
  foreach($numRowsSet as $num_rows):
   $num_pages = $num_rows / $per_page;
   $lastpage = ceil($num_pages);
  endforeach;

Is my num_rows in php done correctly?

Answer 1

You never bothered EXECUTING your query. All you did was stuff some SQL text into a string. mysql_num_rows() expects a MySQL query result handle, which is most definitely not a string.

Try

$sql = "..."
$result = mysql_query($sql) or die(mysql_error());
$numrows = mysql_num_rows($result);

And be warned that the mysql_*() functions are deprecated. You should NOT be using them in any new code. Switch to mysqli (note the i) or PDO.