mysql_fetch_array and array keys

Question

This code works:

$row = array(5,6,89,97,101);
$found = array();
$post = 89;
$count_row = count($row);
for($i = 0; $i < $count_row; $i++){
    if($row[$i]==$post){
        $found[] = $row[$i-2];
        $found[] = $row[$i-1];
        $found[] = $row[$i];
        $found[] = $row[$i+1];
        $found[] = $row[$i+2];
        var_dump($found);
    }
}

And this does not, probably doing something wrong in the mysql_fetch_array;

$found = array();
        $q = "SELECT object_id FROM wp_term_relationships WHERE term_taxonomy_id='$term_tax_id'";
        $rs = mysql_query($q) or die(mysql_error());
        $row = mysql_fetch_array($rs, MYSQL_NUM);
        $count_row = count($row);
        for($i = 0; $i < $count_row; $i++){
        print_r($row);
            if($row[$i]==$post){
                $found[] = $row[$i-2];
                $found[] = $row[$i-1];
                $found[] = $row[$i];
                $found[] = $row[$i+1];
                $found[] = $row[$i+2];
                var_dump($found);
            }
        }

Nothing is shown if post is more than 1. Anyone know a way to solve this problem?

Try print_r($row): what is the output? More: in second example I don't see $found and $post initialization... — Marco
– Marco, Commented Aug 29, 2011 at 12:04
So, your query is wrong or doesn't return what you're expecting I think... If you want us to help you, show us some code !!! — Marco
– Marco, Commented Aug 29, 2011 at 12:09
@Marco Added query, the query works, I've looped it with while and checked. — Muazam
– Muazam, Commented Aug 29, 2011 at 12:12
Any time the body of a loop is an if statement, it's wasteful, especially when the body of the if will only be entered once. If you're only interested in 5 records, fetch only those 5 records. — outis
– outis, Commented Aug 29, 2011 at 12:21

glglgl · Accepted Answer · 2011-08-29 13:21:46Z

mysql_fetch_array() fetches one single row, which, in your case, contains exactly one column.

You should either query all rows from the result set at once (which I don't know how that works), or you should do this:

$q = "SELECT object_id FROM wp_term_relationships WHERE term_taxonomy_id='$term_tax_id'";
$rs = mysql_query($q) or die(mysql_error());
$data = array();
while ($row = mysql_fetch_array($rs, MYSQL_NUM)) {
    $data[] = $row[0];
}
for($i = 2; $i < count($data) - 2; $i++){ // adjusted boundaries
    if($data[$i]==$post){
        $found[] = $data[$i-2];
        $found[] = $data[$i-1];
        $found[] = $data[$i];
        $found[] = $data[$i+1];
        $found[] = $data[$i+2];
        var_dump($found);
    }
}

}

I as well have adjusted the boundaries: if you are interested in the range $i-2 to $i+2, you only should run from 2 to end-2.

The code works almost like I want it. Nothing is shown if the post is less than 4. do you know how to fix that?
Instead of adjusting the boundaries, do a boundary check inside the loop so if you're at $i == 0 don't add $data[$i-2] and $data[$i-1] etc.

outis · Accepted Answer · 2011-08-29 12:57:43Z

The select statement should be rewritten so as to return only the values you're looking for. One way to do this is with a UNION of two selects, one returning lesser object IDs and one returning greater. You should also make use of WordPress's wpdb class. For one thing, a site admin may change the table prefix from "wp_" to something else; $wpdb->term_relationships will give the correct name for the table.

$statement = $wpdb->prepare(
   "  (SELECT object_id 
        FROM $wpdb->term_relationships 
        WHERE term_taxonomy_id= %d 
          AND object_id <= %d
        ORDER BY object_id DESC 
        LIMIT 3)
    UNION
      (SELECT object_id 
        FROM $wpdb->term_relationships 
        WHERE term_taxonomy_id= %d
          AND object_id > %d
        ORDER BY object_id ASC 
        LIMIT 2)
      ORDER BY object_id", $term_tax_id, $post, $term_tax_id, $post);
$found = $wpdb->get_results($statement);

This also has the advantage of working when there are less than two terms relationships before or after the center (the object with id $post).

It seems to work, but I how do I loop them? Thanks! I tried echo $found[0]['object_id'];
No need for the loop to build the result array. wpdb::get_results returns all the results as an array. By default, the items in this array are objects. Set the second arguments of get_results to one of the constants mentioned in the documentation for a different item type. In this specific example, you could instead use wpdb::get_col

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