I've been studying the MySQL documentation and found the following:
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4.16.1 Upgrading from a 3.22  version to a 3.23

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The following lists what you have to watch out for when upgrading to 3.23

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o mysql_num_fields() can no longer be used on a MYSQL* object (it's now a function that takes MYSQL_RES* as an argument. You should now use mysql_field_count() instead.
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It's in the on-line MySQL documentation...

My host shows that we are using PHP 3.06, which isn't in your list, so I selected the 3.0.14 version. They will be upgrading to MySQL 3.23 shortly, so this concerns me that a number of my scripts will break; at least the ones that rely on mysql_num_fields.

Jeff