Why Am I Getting the \"mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource\" Warning in PHP?

"php warning mysql_fetch_assoc": A Mistake

This article delves into the issue of encountering the "mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource" warning when accessing information from a MySQL database using PHP.

Typically, the mysql_* functions in PHP operate in a particular manner, as seen below:

<code class="php">$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
}</code>

In this example, $resource represents a valid MySQL result resource, obtained from executing the query. When this resource is passed to mysql_fetch_assoc, it extracts associative arrays from the result set. However, if something other than a valid result resource is passed to mysql_fetch_assoc (e.g., a string, object, or boolean), the function raises an error.

One common pitfall is passing something other than a valid query string to mysql_query. In such cases, mysql_query will return FALSE, which is not a valid result resource. Attempting to pass FALSE to mysql_fetch_assoc will trigger the warning.

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