Sorting PHP arrays - php

Question

I have three MySQL tables that I need to query for all of the rows. Upon getting all of the rows from each table, I need to create a multidimensional array whereby each index of that array contains only value from each of the tables. What I have right now works. But, something is telling me that there has got to be a better way of accomplishing this.
$tables = array('table_one', 'table_two', 'table_three');
$final = array();
foreach($tables as $table) {
$sql = "SELECT * FROM ".$table."";
$query = mysqli_query($con, $sql)or die(mysqli_error($con));
$num = mysqli_num_rows($query);
$i = 0;
while($row = mysql_fetch_array($query)) {
$id[$i] = $row['user_id'];
$i++;
}
for($i=0;$i<$num;$i++) {
if(!is_array($final[$i])) {
$final[$i] = array($id[$i]);
} else {
array_push($final[$i], $id[$i]);
}
}
}
The end results is something that looks like this
$final = array(array('table_one_row_one_val', 'table_two_row_one_val', 'table_three_row_one_val'),
array('table_one_row_two_val', 'table_two_row_two_val', 'table_three_row_two_val'),
array('table_one_row_three_val', 'table_two_row_three_val', 'table_three_row_three_val')
);
I get the gut felling that this could be done much more effectively, but I'm not sure how.
Thanks,
Lance

Answer 1

You can make your code simpler if you make your query more explicit in selecting the columns you want in the order you want them. So for example:
$sql = 'SELECT table_one.user_id as u1, table_two.user_id as u2, table_three.user_id as u3 FROM ' . implode(',', $tables);
Then each row of your result set will have the columns in the proper order making the construction of your arrays less involved. For example:
$query = mysqli_query($con, $sql)or die(mysqli_error($con));
while($row = mysql_fetch_array($query)) {
$final[] = array($row['u1'], $row['u2'], $row['u3']);
}
There may be issues with the order and relationships of the data in these arrays (especially if all 3 tables don't have the same number of rows), but working just off the information above, this is another way you could approach it. Something to think about anyway.

Answer 2

Try this:
$sql = "SELECT 'user_id' FROM ".$table;

Answer 3

What about:
$tables = array('table_one', 'table_two', 'table_three');
$final = array();
foreach($tables as $tableIndex => $table) {
$sql = "SELECT user_id FROM ".$table;
$query = mysqli_query($con, $sql)or die(mysqli_error($con));
$i = 0;
while($row = mysql_fetch_array($query)) {
$final[$tableIndex][$i] = $row['user_id'];
$i++;
}
}
It is always better selecting only the columns you will use. SELECT * is not a good SQL practice.