mysql_fetch_field not working

Question

I'm running a while loop to print certain data from a table. Because the data for the table is stored in what will become a very large table, I've heard its a good idea to create a separate table that just stores the number of rows of relevant data for this table. I'm trying to implement this, but not having much luck, why isn't the below working?

$numberofrows=mysql_fetch_field(mysql_query("SELECT rows FROM rows WHERE guestlist_id = '$guestlist_id'")) or die();
echo $numberofrows;

The above gives the error: Catchable fatal error: Object of class stdClass could not be converted to string in FULLURL/html/scripts/addname.php on line 36

PS - this query works in phpMyAdmin, so I know the data is there. Thanks!

score 1 · Accepted Answer · answered Mar 08 '12 at 19:03

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Your $numberofrows is an object, you can only output its properties, e.g.:

echo $numberofrows->name;

See: http://php.net/manual/en/function.mysql-fetch-field.php

answered Mar 08 '12 at 19:03

Config

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score 0 · Answer 2 · answered Mar 08 '12 at 19:01

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Please read the PHP documentation.

answered Mar 08 '12 at 19:01

Peter Kiss

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Can you provide me some information abou what is your goal? Becouse your query with this PHP code doesn't make a sense. – Peter Kiss Mar 08 '12 at 19:10
Sure @PeterKiss -I'm building a guest list application that stores the created guest lists in a table called 'lists' and the names for these lists in a table called 'names'. The names added are printed on the guestlist submission page using a while loop. The loop runs – Ryan Brodie Mar 09 '12 at 21:00
... according to a mysql_numrows query. To remove the need for this, I aim to make a table that contains the number of rows of each guest list which can then be used as the value for the while loop, rather than having to run this query, which in turn should speed things up. Any ideas? – Ryan Brodie Mar 09 '12 at 21:02

score 0 · Answer 3 · edited May 23 '17 at 11:55

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$guestlist_id is probably not a string. Make sure it is one before you run the query.

As a side note, you are not doing any error checking, which will make your code a nightmare to debug. Check out this question for advice on how to do proper error checking:

Reference: What is a perfect code sample using the MySQL extension?

edited May 23 '17 at 11:55

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answered Mar 08 '12 at 19:01

Pekka

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It is a string, and I checked by echoing. – Ryan Brodie Mar 09 '12 at 20:58

score 0 · Answer 4 · answered Mar 08 '12 at 19:03

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I've heard its a good idea to create a separate table

That's wrong idea.
Keep your data in a single table.

answered Mar 08 '12 at 19:03

Your Common Sense

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But won't row counting take an age? – Ryan Brodie Mar 09 '12 at 20:57
Nope. Fetching and counting data is the only database purpose. It is designed for that. And doing it well. – Your Common Sense Mar 09 '12 at 21:11
Fetching is quicker than counting, right? Fetching a piece of data, e.g. number_rows = 1, is surely a less intensive operation than running a count on a table with 1000's of entries? – Ryan Brodie Mar 09 '12 at 21:31
@RyanBrodie if data is indexed, counting gets no more time than fetching. – Your Common Sense Mar 10 '12 at 04:19

mysql_fetch_field not working

4 Answers4