Question

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Warning: mysql_fetch_array(): supplied argument is not a valid MySQL result

I’m having a problem with this mysql code. I presume its a basic error in the $sqlx… line but I’m slightly lost.

The code basically prints messages from a db
Here is the code:

$sqls="SELECT username FROM social WHERE `adder`='$username'";
$results=mysql_query($sqls);
$resulti= mysql_num_rows($results);
if ($resulti==0) {
echo "You haven't added anyone yet. Find some <a   href=\"/social/suggestions\">suggestions</a>";
}
$row=mysql_fetch_array($results);

$sqlx="SELECT * FROM messages WHERE `sender` IN ($row)";
$resultx= mysql_query($sqlx); 
$resultz= mysql_num_rows($resultx);
if ($resultz==0){
echo "No messages at all!!";
}
else {
$finished="false";
$r=0;
While(($rowx=mysql_fetch_assoc($resultx))&&($finished=="false")) {
//echo off messages

$username is got further up the file.

Here is the error:

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in /home/user/public_html/social/iframe/index.php on line 34

Line 34 is $resultz= mysql_num_rows($resultx);
But like i said the error is probably the line two up from that.

One interesting happens. “No messages at all!!” is echoed out which means the result of the mysql_query is 0. This is why I am convinced it is the line 32, ($sqlx)

Any idea??

Have I done the mysql_fetch_array wrong when getting $row??
thanks

Answer 1

$row=mysql_fetch_array($results);

$sqlx="SELECT * FROM messages WHERE `sender` IN ($row)";

This will create the following query:

SELECT * FROM messages WHERE `sender` IN (Array)

This is obviously not a valid MySQL query. You have to process the array.

$sqlx = "SELECT * FROM `messages` WHERE `sender` IN ("; // start of query

foreach($row as $r)
    $sqlx .= "'".$r['username']."',"; // insert all returned usernames

$sqlx = substr($sqlx,0,-1).')'; // substract the last comma and close the query

Or, as RiaD pointed out in the comments:

$sqlx = "SELECT * FROM `messages` WHERE `sender` IN (".
        implode(',',array_map(function($x){return "'".$x['username']."'"; }, $row)).
        ")";

PS: Riad, it should be $x['username'] instead of $x and you forgot the semicolon 😉