php substr how to make 2decimals places instead of 4?

[XBOX360 MW2]

my script is showing 4 decimal places ie 8.3423
i only want it to show 2 decimal places ie 8.34

what do i have to change on my script?

this is the script

EOF;

$uSql = "
SELECT
$GLOBALS[TB_IMAGES].image_id as image_id,
$GLOBALS[TB_IMAGES].user_id as user_id,
$GLOBALS[TB_IMAGES].average_rating as average_rating
FROM $GLOBALS[TB_IMAGES]
WHERE image_type_id = '$array[image_type_id]'
AND $GLOBALS[TB_IMAGES].image_status = 'approved'
ORDER BY $GLOBALS[TB_IMAGES].average_rating desc
LIMIT $GLOBALS[SITE_MAX_USER_COUNT_RIGHT_SIDE]
";

$uQuery = sqlQuery( $uSql );

while( $uArray = sqlFetchArray( $uQuery ) )
{
$nbSpace = getSpace( $space + 1 );

$average_rating = $uArray[ 'average_rating' ] == 10
? substr( $uArray[ 'average_rating' ],
0,
strlen( $uArray[ 'average_rating' ] ) -1 )
: $uArray[ 'average_rating' ];

$image_name = getImageName( $uArray[ 'image_id' ], 1 );

$html .= <<<EOF
<tr class="alt2" style="line-height:10pt;">
<td width="98%"><a class="rs" href="index.php?i=$uArray[image_id]">$nbSpace$image_name</a></td>
<td width="2%" class="alt1"><span class="small">*$average_rating*</span></td>
</tr>