Php system rating for photo gallery that allows 1 vote/day for each photo

Question

I'm trying to develop a Php Photo Gallery only for my personal use and I put a Php System Rating using a modified script that I found on the web... all works fine except for one thing, I cannot stop users from posting several votes in the same day! I'd like that users vote the photos (several photos as well) but voting one time in the same day (one vote for each photo)... I post here the script that I have modified.

ratings.php:

<?php
  $rating = new ratings($_POST['widget_id']);
  isset($_POST['fetch']) ? $rating->get_ratings() : $rating->vote();
  class ratings {
    var $data_file = './ratings.data.txt';
    private $widget_id;
    private $data = array();
    function __construct($wid) {
      $this->widget_id = $wid;
      $all = file_get_contents($this->data_file);
      if ($all) {
        $this->data = unserialize($all);
      }
    }
    public function get_ratings() {
      if ($this->data[$this->widget_id]) {
        echo json_encode($this->data[$this->widget_id]);
      } else {
        $data['widget_id'] = $this->widget_id;
        $data['number_votes'] = 0;
        $data['total_points'] = 0;
        $data['dec_avg'] = 0;
        $data['whole_avg'] = 0;
        echo json_encode($data);
      }
    }
    public function vote() {
      # Get the value of the vote
      preg_match('/star_([1-5]{1})/', $_POST['clicked_on'], $match);
      $vote = $match[1];
      $ID = $this->widget_id;
      # Update the record if it exists
      if ($this->data[$ID]) {
        $this->data[$ID]['number_votes'] += 1;
        $this->data[$ID]['total_points'] += $vote;
      } else {  # Create a new one if it doesn't
        $this->data[$ID]['number_votes'] = 1;
        $this->data[$ID]['total_points'] = $vote;
      }
      $this->data[$ID]['dec_avg'] = round($this->data[$ID]['total_points'] / $this->data[$ID]['number_votes'], 1);
      $this->data[$ID]['whole_avg'] = round($this->data[$ID]['dec_avg']);
      file_put_contents($this->data_file, serialize($this->data));
      $this->get_ratings();
    }
    # ---
    # end class
  }
?>

ratings.js:

$(document).ready(function() {
  $('.rate_widget').each(function(i) {
    var widget = this;
    var out_data = {
    widget_id : $(widget).attr('id'),
    fetch: 1
  };
  $.post(
  'ratings/ratings.php',
  out_data,
  function(INFO) {
    $(widget).data('fsr', INFO);
    set_votes(widget);
  },
  'json'
  );
  });
  $('.ratings_stars').hover(
  function() {
    $(this).prevAll().andSelf().addClass('ratings_over');
    $(this).nextAll().removeClass('ratings_vote'); 
  },
  function() {
    $(this).prevAll().andSelf().removeClass('ratings_over');
    set_votes($(this).parent());
    }
  );
  $('.ratings_stars').bind('click', function() {
    var star = this;
    var widget = $(this).parent();
    var clicked_data = {
    clicked_on : $(star).attr('class'),
    widget_id : $(star).parent().attr('id')
  };
  $.post(
  'ratings/ratings.php',
  clicked_data,
  function(INFO) {
  widget.data('fsr', INFO);
  set_votes(widget);
  },
  'json'
  ); 
  });
});
function set_votes(widget) {
  var avg = $(widget).data('fsr').whole_avg;
  var votes = $(widget).data('fsr').number_votes;
  var exact = $(widget).data('fsr').dec_avg;
  window.console && console.log('and now in set_votes, it thinks the fsr is ' + $(widget).data('fsr').number_votes);
  $(widget).find('.star_' + avg).prevAll().andSelf().addClass('ratings_vote');
  $(widget).find('.star_' + avg).nextAll().removeClass('ratings_vote'); 
  $(widget).find('.total_votes').text( votes + ' votes (' + exact + ' rating)' );
}

I tried to implement IP mechanism in ratings.php as below without lucky

<?php
  $rating = new ratings($_POST['widget_id']);
  isset($_POST['fetch']) ? $rating->get_ratings() : $rating->vote();
  class ratings {
    var $data_file = './ratings.data.txt';
    private $widget_id;
    private $data = array();
    function __construct($wid) {
      $this->widget_id = $wid;
      $all = file_get_contents($this->data_file);
      if ($all) {
        $this->data = unserialize($all);
      }
    }
    public function get_ratings() {
      if ($this->data[$this->widget_id]) {
        echo json_encode($this->data[$this->widget_id]);
      } else {
        $data['widget_id'] = $this->widget_id;
        $data['number_votes'] = 0;
        $data['total_points'] = 0;
        $data['dec_avg'] = 0;
        $data['whole_avg'] = 0;
        echo json_encode($data);
      }
    }
    public function vote() {
      # Get the value of the vote
      preg_match('/star_([1-5]{1})/', $_POST['clicked_on'], $match);
      $vote = $match[1];
      $ID = $this->widget_id;
      # Update the record if it exists
      if ($this->data[$ID]) {
        $this->data[$ID]['number_votes'] += 1;
        $this->data[$ID]['total_points'] += $vote;
        $this->data[$ID]['remote_ip'] = $_SERVER['REMOTE_ADDR'];
      } else {  # Create a new one if it doesn't
        $this->data[$ID]['number_votes'] = 1;
        $this->data[$ID]['total_points'] = $vote;
        $this->data[$ID]['remote_ip'] = $_SERVER['REMOTE_ADDR'];
      }
      if ($this->data[$ID]['remote_ip'] != $_SERVER['REMOTE_ADDR']) {
        $this->data[$ID]['dec_avg'] = round($this->data[$ID]['total_points'] / $this->data[$ID]['number_votes'], 1);
        $this->data[$ID]['whole_avg'] = round($this->data[$ID]['dec_avg']);
        file_put_contents($this->data_file, serialize($this->data));
        $this->get_ratings();
      }
    }
    # ---
    # end class
  }
?>

Answer 1

The simplest way is to notify in a data table who vote and which day.

For example : Toto vote on 2014-07-04, so he can't vote twice today.

In data table user you add a colum date to notify the last day of vote.

You can use cookies but it's very very ugly !