Вот грязный путь:
$contents = ' /SV/temp_images/766321929_2.jpg';
$contents = substr($contents, strpos($contents, 'temp_images/'));
$contents = substr($contents, strpos($contents, '/'));
$contents = substr($contents, 1);
$contents = substr($contents, 0, strpos($contents, '_'));
print $contents;