<a href="#" data-page=[12,3]></a>
<a href="#" data-page=[12,2]></a>
$pattern = '/data-(\w+)=/';
$string = '<strong class="annotate annotateSelected" data-pageid="1242799" data-start="80" data-end="86" data-canon="Season" data-toggle="tooltip" title="Season (SPORTS_OBJECT_EVENT)" data-placement="top" data-type="SPORTS_OBJECT_EVENT"><em>season</em></strong>';
preg_match_all($pattern,$string,$result);
$arr = array();
foreach($result[1] as $item){
$pat = '/data-'.$item.'="(?P<'.$item.'>\w+?)"/';
preg_match($pat, $string, $res);
$arr[$item] = $res[1];
}
echo print_r($arr);
Array
(
[pageid] => 1242799
[start] => 80
[end] => 86
[canon] => Season
[toggle] => tooltip
[placement] => top
[type] => SPORTS_OBJECT_EVENT
)