You'll learn how to identify the failed MySQL query behind the "expects parameter 1 to be resource" warning and fix it using modern, reliable PHP database code.

Time needed: Approximately 10–20 minutes.

If you're maintaining an older PHP application, you may encounter an error like this:

Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given

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The same warning can appear with several functions:

mysql_fetch_assoc() expects parameter 1 to be resource mysql_fetch_row() expects parameter 1 to be resource mysql_num_rows() expects parameter 1 to be resource

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These warnings usually have one underlying cause: the SQL query failed, but the application tried to read its result anyway.

The fetch function is where the problem becomes visible.…