javascript - jQuery post callback function set variable returning nothing -

i trying use localstorage variable in php function decided use jquery post() so. afterwards, want echo data original file , set inside global variable. have 3 files connect each other (its bit complicated).

quick_match.php

  datastring = ""; $.post("ajaxctrl.php", {action: "doquickmatch", numcard: localstorage['numcard'], ui: "<?php echo $_request['ui']; ?>"}, function(data){ datastring = data; }); 

ajaxctrl.php

if($action == "doquickmatch") {     //start quick match     $result = $user->getquickmatch($numcard);     echo $result; } 

user.php

  (a big query here guarantee works)    // perform query   $result = mysql_query($query);    //hold array objects in string   $string = "";   // iterate through results , print   while ($row = mysql_fetch_assoc($result)) {     $string .= '{ image: \'http://personals.poz.com'.$row['my_photo'].'\', user_id: \''.$row['id'].'\', user_prof: \'http://127.0.0.1/personalz.poz/v2/member.php?username='.$row['id'].'\'};';   }   return $string; 

after of this, i'm supposed use string , split can array , continue on doing. however, callback keeps on returning nothing not sure did wrong. can offer insight please? thank in advance.