$wpdb->update

I realized I was missing a comma and don’t seem to need the single quotes on the field names, but I’m still getting the same error. Here is my updated line of code:

$wpdb->update('wp_network_members', $insert_member_data, WHERE f_name = $insert_member_data['f_name'] AND l_name = $insert_member_data['l_name']);

Try popping the clause in a variable first?

$where = "WHERE f_name = {$insert_member_data['f_name']} AND l_name = {$insert_member_data['l_name']}'"
$wpdb->update('wp_network_members', $insert_member_data, $where);

Could do with seeing an example of what’s in the $insert_member_data array, obviously
aside from f_name and l_name.

That said, i think the update should look something like this..

$wpdb->update(
    'wp_network_members', // Table
    $insert_member_data, // Array of key(col) => val(value to update to)
    array(
        'f_name' => $insert_member_data['f_name'],
        'l_name' => $insert_member_data['l_name']
    ) // Where
);

..which should be inline with the example here.
https://codex.www.ads-software.com/Function_Reference/wpdb_Class#Examples_7

Without knowing more about what’s in $insert_member_data though it’s hard to say if the query needs further adjustment(it will do if any the columns you’re updating are numeric columns – or something not a string).

You might find it easier to use $wpdb->query alongside $wpdb->prepare, so you can do your own UPDATE foo WHERE bar, etc.. without the fiddly formats you’d have to contend with using $wpdb->update.

I found the solution – I replaced the two items that the WHERE statement was using with an array of the two values and now it works fine.

Example:

$wpdb->update('wp_network_members', $insert_member_data, $insert_member_data_match);