Stocking user visited pages in a serialized array Mysql php : strangely disapearing -

i stock page user has visit in serialized array in database. when visitor has visited few page (~60 or more) array disapear , restarts 0. how fix ?

thank !

my code

    if($utilisateur[0]!=null) {      $table=unserialize($_session['vue']); if($table[$_get["serie"]][$_get["version"].round($_get["numero"]/64)]!=null) { } else { $table[$_get["serie"]][$_get["version"].round($_get["numero"]/64)]=0; }     if($table[$_get["serie"]][$_get["version"].round($_get["numero"]/64)]&pow(2,($_get["numero"]%64)))     {     }    else    {        $table[$_get["serie"]][$_get["version"].round($_get["numero"]/64)]=$table[$_get["serie"]][$_get["version"].round($_get["numero"]/64)]|pow(2,($_get["numero"]%64)) ;      $_session['vue']=serialize($table);      $req2 = $loginbase->prepare('update `user` set vue = ? utilisateur = ?'); $req2->execute(array($_session['vue'],$utilisateur[0]));      }   } 

i have series (video) , use binar operation tell witch episode has been visited because of int leght have change name if episode higher 64 because int stock 64 bites ... if not clear ask. $utilisateur array stock user data , have save info in session