MySQL:Obtenha um resultado de retorno de um INSERT SELECT

<?php
$pdo = new PDO('mysql:host=localhost;dbname=test;charset=utf8', 'localonly', 'localonly');
$pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
$pdo->setAttribute(PDO::ATTR_EMULATE_PREPARES, false);
setup($pdo);

$query = "
    INSERT INTO tbl1 (myID, myVal1, myVal2)
    SELECT @foo:=myID+1, 'val1', 'val2' FROM tbl2 WHERE x=0 LIMIT 1
";
$pdo->exec($query);
foreach( $pdo->query('SELECT @foo as foo') as $row ) {
    echo $row['foo'];
}


function setup($pdo) {
    $pdo->exec('CREATE TEMPORARY TABLE tbl1 (myID int, myVal1 varchar(16), myVal2 varchar(16))');
    $pdo->exec('CREATE TEMPORARY TABLE tbl2 (myID int, x int)');
    $pdo->exec('INSERT INTO tbl2 (myID, x) VALUES (1,1),(2,1),(3,0),(4,0),(5,1)');
}