mysql_fetch_array()/mysql_fetch_assoc()/mysql_fetch_row()/mysql_num_rows etc… expects parameter 1 to be resource

Question

I am trying to select data from a MySQL table, but I get one of the following error messages:

mysql_fetch_array() expects parameter 1 to be resource,

Answer 1

$result = mysql_query('SELECT * FROM Users WHERE UserName LIKE $username');

You define the string using single quotes and PHP does not parse single quote delimited strings. In order to obtain variable interpolation you will need to use double quotes OR string concatenation (or a combination there of). See http://php.net/manual/en/language.types.string.php for more information.

Also you should check that mysql_query returned a valid result resource, otherwise fetch_*, num_rows, etc will not work on the result as is not a result! IE:

$username = $_POST['username'];
$password = $_POST['password'];
$result = mysql_query('SELECT * FROM Users WHERE UserName LIKE $username');

if( $result === FALSE ) {
   trigger_error('Query failed returning error: '. mysql_error(),E_USER_ERROR);
} else {
   while( $row = mysql_fetch_array($result) ) {
      echo $row['username'];
   }
}

http://us.php.net/manual/en/function.mysql-query.php for more information.