Display column values from database - php

Question

I'm trying to display all the values from a specific column created by my Wordpress plugin (specifically, the ID's). Here is the code I have managed to use to display the column names, but I cannot get it to just display all the ID's. Here is the code:
function test() {
global $wpdb;
global $table_name;
$testing = $wpdb->get_col_info('name', 0);
foreach ($testing as $test) {
echo $test;
}
}
And here you can see the output:
www.matthewruddy.com/premiumslider
Can anyone help me out?

Answer 1

It seems you want data instead of column information. So you need to another function.
$testing = $wpdb->get_results("SELECT id FROM mytable")
foreach ($testing as $test) {
echo $test->id
}
EDIT:
OK, how about this one:
$wpdb->show_errors();
echo 'Listing from table: $table_name<br>';
$ids = $wpdb->get_col($wpdb->prepare("SELECT id FROM %s", $table_name));
if ($ids) {
echo 'printing results:<br>';
foreach($ids as $id) {
echo $id;
}
} else {
echo 'no results or error<br>';
echo 'error: ' . $wpdb->print_error();
}
$wpdb->hide_errors();
If this doesn't help you either to get your ID's or to figure out what the error is, I am lost.

Answer 2

Might be a little late for this question, but I think it is still relevant to todays WordPress world and also a situation I ran into creating my own plugin.
So for anyone else, this worked for me. The OP almost had it. However, $wpdb->get_col_info() relies on a cache result for its results so a $wpdb->get_results or get_row or query needed to be called first. :)
I also liked littlegreen's error handling.
function test() {
global $wpdb, $table_name;
$wpdb->show_errors();
$return = 'Listing from table: '.$table_name.'';
$results = $wpdb->get_results("SELECT * FROM ".$table_name);
$nameCols = $wpdb->get_col_info('name');
if (is_array($nameCols)) {
$return .= 'printing results:';
foreach($nameCols as $name) {
$return .= ' '.$name;
}
} else {
$return .= 'no results or error'.
'error: ' . $wpdb->print_error();
}
$wpdb->hide_errors();
}