var app = {

initialize: function() {
    this.bindEvents();
},

bindEvents: function() {
    document.addEventListener('deviceready', this.onDeviceReady, false);
},

onDeviceReady: function() {
    var push = PushNotification.init({
        "android": {
            "senderID": "xxxxxxxxx"
        },
        "ios": {"alert": "true", "badge": "true", "sound": "true"},
        "windows": {}
    });

    push.on('registration', function(data) {
        console.log("registration event");
        var gcm_regid = data.registrationId;
        $.post('http://xxxxx.xxx/insert.php', {gcm_regid: gcm_regid});
 return false;
    });

<?php
$con = mysql_connect("localhost","gcm","password");
if (!$con) {
die('Could not connect: ' . mysql_error());
}
mysql_select_db("gcm", $con);
$gcm_regid=$_POST['gcm_regid'];

  $query=mysql_query("INSERT INTO gcm_users(gcm_regid) VALUES('$gcm_regid')");
     if($query){
  echo "Data for $gcm_regid inserted successfully!";
  }
 else{ echo "An error occurred!"; }
  ?>

id  -> int(11) -->  AUTO_INCREMENT
gcm_regid   text
created_at -->  timestamp -> CURRENT_TIMESTAMP

ALTER IGNORE TABLE gcm_users
ADD UNIQUE INDEX idx_name (gcm_regid);