In your query, specify the columns that you want to populate, for example:
$stmt = $conn->prepare('INSERT INTO project (category, title, name) VALUES(:category, :title, :name)');
If you don't specify the columns in that way, you have to include a value for all columns in the table, that's why you're getting the error - because there are other columns in the table and you haven't explicitly specified a value for them all.
It is better to specify the columns because if any columns are added or the order is changed in future, your query will break unless the column list is specified.
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