在里面获取MySQL语句的下一个值

Question

I'm putting values from the database inside a while into an array. Now I wan't to check - inside the while - if the next ID is the same as just outputed. If it isn't my thought is to put the ID inside the array.

Is there any possibility to do this? To check a the next output of a query in a while?

$result = mysql_query("SELECT * FROM $postmeta ORDER BY post_id ASC") 
or die(mysql_error());

$basArray = array();    

while($row = mysql_fetch_array( $result )) {

    $innerArray[$row['meta_key']] = $row['meta_value'];     
    $basArray[$row['post_id']] = $innerArray;
// Above post_id I want to check if it is the same as the "next coming"

}

Greetings

Answer 1

I would usually just store the most recent ID in a variable, and check it at the top of the while loop. In pseudocode, like this:

$old_row_id = -1; // any value that can't legitimately appear
while ($row = fetch_array($result)) {
    if ($old_row_id == $row['id']) {
        // logic to follow if IDs are the same
    } else {
        // logic to follow if IDs are different
    }
    // logic to follow in either case, if any
    $old_row_id = $row['id']; // update variable for the next run through
}

If you really do need to change the behaviour for a particular row according to what happens in the next row, I recommend that you actually effect that change in the following run through the loop, when you check the new row ID against the old one.

Alternatively, you can loop through the resultset twice: the first time putting the rows into a 2-dimensional array so that you can easily reference difference rows by number. Then the second time, you actually do whatever you wanted to do in the first place, and you can reference "the next row" by using [$i + 1] rather than [$i]. (Of course then you have to be careful about the final row, because then the offset [$i + 1] doesn't work.)