$tabcn = array ('nom' => $row['nom'], 'nbs' => $row['nbsaisons'], 'nbm' => $totmatchs, 'nbb' => $totbuts);

$tabtabcn[$i] = $tabcn;

<?php
$tabtabcn[] = array ('nom' => 'ligne 1', 'nbs' => 1, 'nbm' => 56, 'nbb' => 12);
$tabtabcn[] = array ('nom' => 'ligne 2', 'nbs' => 2, 'nbm' => 45, 'nbb' => 48);
$tabtabcn[] = array ('nom' => 'ligne 3', 'nbs' =>3, 'nbm' => 78, 'nbb' => 8);
$tabtabcn[] = array ('nom' => 'l 4', 'nbs' => 4, 'nbm' => 156, 'nbb' => 0);
$tabtabcn[] = array ('nom' => 'l5', 'nbs' => 5, 'nbm' => 456, 'nbb' => 115);
$tabtabcn[] = array ('nom' => 'L 6', 'nbs' => 6, 'nbm' => 464, 'nbb' => 34);
var_dump($tabtabcn);
echo '<hr />';
foreach ($tabtabcn as $key => $row) {
    $nom[$key] = $row['nom'];
    $nbs[$key] = $row['nbs'];
    $nbm[$key] = $row['nbm'];
    $nbb[$key] = $row['nbb'];
}
array_multisort($nbb,SORT_DESC,$tabtabcn);
var_dump($tabtabcn);
?>

array
0 =>
array
'nom' => string 'l5' (length=2)
'nbs' => int 5
'nbm' => int 456
'nbb' => int 115
1 =>
array
'nom' => string 'ligne 2' (length=7)
'nbs' => int 2
'nbm' => int 45
'nbb' => int 48
2 =>
array
'nom' => string 'L 6' (length=3)
'nbs' => int 6
'nbm' => int 464
'nbb' => int 34
3 =>
array
'nom' => string 'ligne 1' (length=7)
'nbs' => int 1
'nbm' => int 56
'nbb' => int 12
4 =>
array
'nom' => string 'ligne 3' (length=7)
'nbs' => int 3
'nbm' => int 78
'nbb' => int 8
5 =>
array
'nom' => string 'l 4' (length=3)
'nbs' => int 4
'nbm' => int 156
'nbb' => int 0