Set MySQL Variables with MySQLi (not PHP variables

问题:

It's work with PHP variables:

Prepearing one result from query function

   extract($GLOBALS);
   $GLOBALS['mysqli'] = $mysqli;

function select($a,$b){
    $mysqli = $GLOBALS['mysqli'];

    $query = $mysqli -> query($b);
       while($row = ($query -> fetch_assoc())){
        return $row[$a]."<br>";
        }// while
    $query -> free();       
    }

order from where clicked

$self = "SELECT order FROM channels WHERE id='$id'";
$self = "(SELECT order FROM (($self)AS x))";

    if($btn == "Up"){
    // Order previows
    $other = "SELECT MAX(order) FROM channels WHERE order < $self";
        }
    if($btn == "Down"){
    // Order next
    $other = "SELECT MIN(order) FROM channels WHERE order > $self";
        }

$other = "SELECT order FROM channels WHERE order=($other)";

SET PHP VARIABLE INSTEAD OF MYSQL VARIABLE $other = select('order',$other);

$query = "UPDATE channels SET order=$self WHERE order='$other';";
$query .= "UPDATE channels SET order='$other' WHERE id='$id'";

$mysqli->multi_query($query);

The problem? I need a faster query using one MySQL query

This doesnt' work:

SET MYSQL VARIABLE INSTEAD O PHP VARIABLE

$query = "DEFINE other INT;"; // return: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DEFINE other INT(...);
$query .= "DECLARE other INT;"; // return: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'DECLARE other INT(...);
$query .= "SET other = $other;"; // return: Unknown system variable 'other'
$query .= "UPDATE channels SET order=$self WHERE order=other;";
$query .= "UPDATE channels SET order=other WHERE id='$id'";

$mysqli->multi_query($query);

回答1:

You've got to use a user defined variable:

User-Defined Variables

You can store a value in a user-defined variable in one statement and then refer to it later in another statement. This enables you to pass values from one statement to another. User-defined variables are session-specific. That is, a user variable defined by one client cannot be seen or used by other clients. All variables for a given client session are automatically freed when that client exits.

User variables are written as @var_name, where the variable name var_name consists of alphanumeric characters, “.”, “_”, and “$”. A user variable name can contain other characters if you quote it as a string or identifier (for example, @'my-var', @"my-var", or @my-var).

$query .= "SET @other = $other;"; // return: Unknown system variable 'other'