php warning mysql_fetch_assoc

Question

I am trying to access some information from mysql, but am getting the warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource for the second line of code below, any help would be much appreciated.

$musicfiles=getmusicfiles($records['m_id']);
$mus=mysql_fetch_assoc($musicfiles);
for($j=0;$j<2;$j++)
{
 if(file_exists($mus['musicpath']))
 {
  echo '<a href="'.$mus['musicpath'].'">'.$mus['musicname'].'</a>';    
 }
 else
 {
  echo 'Hello world';     
 }
}

function getmusicfiles($m_id)
{
$music="select * from music WHERE itemid=".$s_id;
$result=getQuery($music,$l);
return $result;
}

Answer 1

Without seeing the code of getmusicfiles there's not a lot we can really help you with. You should be returning a valid mysql resource in that function.

Answer 2

it depends of what exactly getmusicfiles() does. it must return a result of mysql_query() function call, then it will be a "valid MySQL result". And you most probably wanted to put the line "$mus=mysql_fetch_assoc($musicfiles)" inside of the "for" cycle to fetch several rows one after another.

Answer 3

Generally, the mysql_* functions are used as follows:

$id = 1234;
$query = 'SELECT name, genre FROM sometable WHERE id=' . $id;
// $query is a string with the MySQL query
$resource = mysql_query($query);
// $resource is a *MySQL result resource* - a mere link to the result set
while ($row = mysql_fetch_assoc($resource)) { 
    // $row is an associative array from the result set
    print_r($row);
    // do something with $row
}

If you pass something to mysql_fetch_assoc that is not a MySQL result resource (whether it's a string, an object, or a boolean), the function will complain that it doesn't know what to do with the parameter; which is exactly what you are seeing.

A common gotcha: you get this warning if you pass something (other than a valid query string) to mysql_query:

$id = null;
$query = 'SELECT name, genre FROM sometable WHERE id=' . $id;
$res = mysql_query($query); 
// $res === FALSE because the query was invalid
// ( "SELECT name, genre FROM sometable WHERE id=" is not a valid query )
mysql_fetch_assoc($res); 
// Warning: don't know what to do with FALSE, as it's not a MySQL result resource

Answer 4

As others have noted, you need to return a valid mysql resource into the mysql_fetch_assoc function to retrieve the next row. For example:

$sql = "select * from table";

$resultSet = mysql_query($sql) or die("Couldn't query the database.");
echo "Num Rows: " . mysql_num_rows($resultSet);

while ($resultRowArr = mysql_fetch_assoc($resultSet)) {
    ...
}

Answer 5

I think you need to specify what the function getQuery()

$result=getQuery($music,$l);

does

Answer 6

function getmusicfiles($m_id) { $music="select * from music WHERE itemid=".$s_id;

$m_id != $s_id ??