Tuesday, April 5, 2016

DIV mask layer not fully covered on top when there is a scroll bar

It's common to create a "mask" layer on top of the page in order to display photos, pop-up messages, etc.

I used to use the "absolute" positioning to do the job under I lately discovered the so called "masked" will move if there is a scroll bar (when shrinking the window's size).

This problem can be easily solved by just setting the DIV to "fixed" position.

Another problem solved! But wait a minute. This solution doesn't work in IE! Let me see if there is a workaround for this...
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Best Way to Round Up Numbers Using Javascript

I previously found several solutions to round up (float) numbers to closest two decimal places. Some are using complicated function with sofisticated codes but I find this one-liner quite effective and efficient:

Math.round(num*100)/100; // for two decimal places
Math.round(num*1000)/1000; // for three decimal places
.
.

I appreciate the author who did this and sorry for forgetting where I get it from.
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Wednesday, March 16, 2016

Login with Facebook using PHP with v5 SDK

It has been a long time since my last post about Facebook. Many things have changed since. This time I want to talk about the new version of Login PHP SDK for Facebook.

The latest version of SDK can be found here.

I think I can skip to codes directly as all the steps to install the SDK and obtain the app_id and app_secret can be easily found in the internet. But I need to point out the errors you may see if something goes wrong. If you see the following error:

Parse error: syntax error, unexpected '[', expecting ')' in ...

You need a PHP 5.4 or higher version to avoid this error.

Instead, if you see this:

Cross-site request forgery validation failed. The "state" param from the URL and session do not match.

It means your app_id and app_secret are not registered to run in the current domain.

Facebook required us to run the login authorization process in two parts: the login link page and the call-back page. The login page will produce a link with new access token to comply with OAuth 2.0 flow. The next page is to process the call-back from Facebook with valid access token so as to do anything with the verified login such as accessing the ID or email address.

As my philosophy is always to make things short and simple as programmers will not like anything too windy, I combined the two parts into one PHP script. Here is the hybrid script:

<?php

session_start();

require_once __DIR__ . '/facebookV5/autoload.php'; // Please point to your facebook SDK autoload.php

$fb = new Facebook\Facebook([
  'app_id' => 'Your App ID',
  'app_secret' => 'Your App Secret',
  'default_graph_version' => 'v2.5',
]);



if (!isset($_GET['code'])) { // If it is a callback, you will get 'code' as query string.

  $helper = $fb->getRedirectLoginHelper();

  $myURL = '{Your Login URL}'; // The URL to this very script such as http://yourdomainname.com/this_hybrid_login_script.php
  $permissions = ['email']; // Optional permissions
  $loginUrl = $helper->getLoginUrl($myURL, $permissions);

  //header( 'Location: ' . htmlspecialchars($loginUrl) ); PLEASE DO USE REDIRECT WITH PHP HEADER! Somehow it doesn't work well with Facebook OAuth 2.0 flow
  echo("<meta http-equiv='refresh' content=\"0;URL='". htmlspecialchars($loginUrl) ."'\" />");
  exit;
}
else { // This is the call-back section:

  $helper = $fb->getRedirectLoginHelper();
  try {
    $accessToken = $helper->getAccessToken();
  } catch( Facebook\Exceptions\FacebookSDKException $e ) {
    echo $e->getMessage();
    exit;
  }

  if (isset($accessToken)) {
    $_SESSION['facebook_access_token'] = ( string ) $accessToken;

    $fb->setDefaultAccessToken($accessToken);

    try {
      $response = $fb->get('/me?fields=email');
      $userNode = $response->getGraphUser();
    } catch(Facebook\Exceptions\FacebookResponseException $e) {
      echo 'Graph returned an error: ' . $e->getMessage();
      exit;
    } catch(Facebook\Exceptions\FacebookSDKException $e) {
      echo 'Facebook SDK returned an error: ' . $e->getMessage();
      exit;
    }

    $me = $response->getGraphUser();
    echo "Your Facebook Email: ".$me->getProperty('email');

    // You now can use the email for the rest of the login process

    exit;
  }
  else if ( $helper->getError() ) {

    // Facebook Login Error

    echo( $helper->getError()."<br>" );
    echo( $helper->getErrorCode()."<br>" );
    echo( $helper->getErrorReason()."<br>" );
    echo( $helper->getErrorDescription()."<br>" );
    exit;
  }

  echo("Access Token cannot be obtained.");
  // You need to debug if you see this as it shouldn't reach here.
  exit;
}

?>


This is a 2-in-1 script. I use the query string 'code' as a signal to decide where it is a call-back from Facebook or it is the first-run before linking to Facebook. If everything goes well and your browser has not run this PHP code before, you will encounter a page where Facebook will ask for your permission to run this PHP app. Here is an example of how it looks like:



After continuing this authorization process, you will not see this page again unless you change the app_id and app_secret. Enjoy logging in with Facebook!

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Monday, March 7, 2016

Limit a DIV to Certain Scroll Height with Javascript

This is very popular nowadays. You can see major websites around the internet are having this feature. Why? Important information will not get left out if the web page is scrolled down a lot. This can improve the navigation experience of the website substantially. So how is it done? You may need to know how to fix a DIV before you can fully understand this post. Here are some of my earlier posts related to this subject:

http://webtrick101.blogspot.my/2015/11/fixing-several-divs-at-same-time-for.html
http://webtrick101.blogspot.my/2015/11/fix- div-on-top-of-page-only-after.html
http://webtrick101.blogspot.my/2015/11/fix-position-of-div-at-bottom-of-page.html

Here are the codes for this post:

<!DOCTYPE HTML>
<html>
<style type="text/css">

#fixbot {
bottom:0px;
position: fixed;
}

#fixright {
right:0px;
position: absolute;
}

#fixtop {
top:0px;
position: fixed;
}

</style>

<script>

var offset;

window.onscroll = function() {

 if (typeof(window.pageYOffset) == 'number') {
  offset = window.pageYOffset;
 }
 else if (document.documentElement) {
  offset = document.documentElement.scrollTop;
 }
 else if (document.body) {
  offset = document.body.scrollTop;
 }
 if (offset > 170) {
  document.getElementById('fixright').style.position = 'fixed';
  document.getElementById('fixright').style.top = '170px';
 }
 else {
  document.getElementById('fixright').style.position = 'absolute';
  document.getElementById('fixright').style.top = '50%';
 }
 document.getElementById('notice').innerHTML = offset;
}

</script>

<body bgcolor="#aabbcc" marginheight=0 marginwidth=0 leftmargin=0 topmargin=0 rightmargin=0 bottommargin=0 onload="window.scrollTo(0,0);">

<div id="fixbot" style="border:0px solid #333; width:100%; height:50px; background-color:#ddd; text-align:center; padding:0px; ">
<p>Hello I am at the bottom!</p>
</div>

<div id="fixright" style="border:0px; width:100px; height:200px; text-align:center; padding:0px; top: 50%; margin-top: -100px; background-color:#cba;">
<table width=100% height=100%><tr><td valign=middle><p>Right!</p></td></tr></table>
</div>

<div id="fixtop" style="border:0px solid #333; width:100%; height:70px; background-color:#ddd; text-align:center; padding:0px; "> <p>Hello I am at the top! <span id="notice"></span></p>
</div>

<table width="95%" align=center><tr><td>
<br>line 1<br>line 2<br>line 3<br>line 4<br>line 5<br>line 6<br>line 7<br>line 8<br>line 9<br>line 10 <br>line 11<br>line 12<br>line 13<br>line 14<br>line 15<br>line 16<br>line 17<br>line 18<br>line 19<br>line 20 <br>line 21<br>line 22<br>line 23<br>line 24<br>line 25<br>line 26<br>line 27<br>line 28<br>line 29<br>line 30 <br>line 31<br>line 32<br>line 33<br>line 34<br>line 35<br>line 36<br>line 37<br>line 38<br>line 39<br>line 40 <br>line 41<br>line 42<br>line 43<br>line 44<br>line 45<br>line 46<br>line 47<br>line 48<br>line 49<br>line 50 <br>line 51<br>line 52<br>line 53<br>line 54<br>line 55<br>line 56<br>line 57<br>line 58<br>line 59<br>line 60 <br>line 61<br>line 62<br>line 63<br>line 64<br>line 65<br>line 66<br>line 67<br>line 68<br>line 69<br>line 70 </td></tr></table>

<script>
setTimeout(function() {window.scrollTo(0, 0);},100); // To make sure when the page is reloaded, the scroll is back to 0
document.getElementById('fixright').style.top = '50%';

</script>

</body>
</html>




In order to position a DIV on the middle of the right hand side, I prepare the DIV to be always 50% of the total height and the - 100px margin (derived from half of the total height of the DIV which is 200px in this case). In this example, I want to fix the right hand DIV to be exactly 70x from the top of the page. I need to let the Javascript to do the job for me by checking the mouse scroll offset. The magic 170px limit can be obtained from adding the half of the total height of the DIV with the target height limit.



The Javascript will detect the scroll offset if it crosses the 170px marking I set. If it is more than the 170px limit, fix the DIV. If it is less, let it scroll as it should be but maintain the 50% position relative to the viewable height of the website window.



One thing to pay attention is when the page is reloaded, the scroll has to go back to 0 or the calibration of the mechanism of these will be off. If this is not desired, one can consider resorting to cookie to track the relative position of the DIV and scroll offset. This is a head start to such new web feature. More complex feature can still be incorporated into these codes such as managing a very long (high) DIV. Enjoy!

Here is the animated demonstration of this example:



Read More »

Wednesday, February 24, 2016

Good Looking HTML Table Style


Creating a good looking HTML table sounds easy but when it comes to actual execution, it is not as easy as it seems. Consider the following most basic HTML textbook codes for a 3x3 HTML table:

<table border=1>
<tr><td>Apple</td><td>Book</td><td>Car</td></tr>
<tr><td>1</td><td>2</td><td>3</td></tr>
<tr><td>4</td><td>5</td><td>6</td></tr>
</table>

Here is how it looks:



This basic table looks unprofessional at the first glance. How about making it with less or thinner border?


<table border=0 cellspacing=0 cellpadding=0>

<tr><td style="border:1px solid #aaa">Apple</td><td style="border:1px solid #aaa">Book</td><td style="border:1px solid #aaa">Car</td></tr>
<tr><td style="border:1px solid #aaa">1</td><td style="border:1px solid #aaa">2</td><td style="border:1px solid #aaa">3</td></tr>
<tr><td style="border:1px solid #aaa">4</td><td style="border:1px solid #aaa">5</td><td style="border:1px solid #aaa">6</td></tr>

</table>

Here it the screen capture of how it looks again:



By disabling the border for entire table and enabling border styling for each individual cell (highlighted in green), the border looks thinner now. But the problem now is the different thickness for the lines. The lines within the box seems thicker than those on the far out. This is due to the double border problem. Those with thicker line came from the neighboring cell borders. Now the next example will demonstrate how to eliminate the redundant lines using CSS:

<table border=0 cellspacing=0 cellpadding=0 style="border-collapse: collapse;">

<tr><td style="border:1px solid #aaa">Apple</td><td style="border:1px solid #aaa">Book</td><td style="border:1px solid #aaa">Car</td></tr>
<tr><td style="border:1px solid #aaa">1</td><td style="border:1px solid #aaa">2</td><td style="border:1px solid #aaa">3</td></tr>
<tr><td style="border:1px solid #aaa">4</td><td style="border:1px solid #aaa">5</td><td style="border:1px solid #aaa">6</td></tr>

</table>

Finally, this looks good:



Setting CSS border-collapse property to collapse now solved the problem. The problem now is the huge number of codes just for a simple 3x3 table. The codes will look complicated when it comes to large table. Now the CSS styling comes into play to simply the coding:

<html>
<style type="text/css">
.s1 {font-family: arial; font-size: 13px; padding: 12px; border-collapse: collapse; }
.s1 td { padding: 5px; border: 1px solid #aaa; text-align: center; }
</style>


<body>

<table class=s1>
<tr><td>Apple</td><td>Book</td><td>Car</td></tr>
<tr><td>1</td><td>2</td><td>3</td></tr>
<tr><td>4</td><td>5</td><td>6</td></tr>
</table>

</body>
</html>

It now looks more prefessional:



Now the table looks much better. Please note that those in green are the extra CSS styles to apply spacing, alignment and font to the table. With these extra settings, the table looks even better! Now you have it, enjoy!
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Thursday, December 31, 2015

Problem Installing phpBB 3.1 Forum on IIS7 Machine


Anyone having this problem? I tried to install this latest phpBB free web forum into my Windows 7 IIS7 PC but I get this error page:



I then download the earlier version which is 3.0 by clicking on a small button on upper right corner:



After running 3.0 version in the localhost, it works fine:



Anyone having this problem on IIS7 machine before? Maybe switching back to older version is the only solution to this?

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Simple Captcha Verification Using Javascript and PHP with GD Lib


This is a simple version that uses minimal amount of codes. However, this practice is not suitable for websites that require stringent security protection.

The PHP codes make use of the GD library to generate a PNG image file that will be read by the HTML code. The PHP will randomly generate two characters and two numbers with first digit as character followed by a number, then a character and a number. Of course, you can change it to something more complicated like making it a mathematical problem to be solved by the visitor. The PNG image will be accompanied by a browser cookie with the answer to the captcha. The cookie will then be compared with the input by the user to see if they match. You can also send the answer back to the server to be verified in order to make it more secure. However, it is not the scope of this example as I try to make it as simple as possible so that it is easy to understand.

Here are the PHP codes:

<?php

// I name this file captcha.php
error_reporting(0); // this is important to turn off all the warnings if any

session_start();

$angle = rand(-10,10);
$fontSize = 20;

$captchaText = chr(97 + rand(0, 25)).rand(0,9).chr(97 + rand(0, 25)).rand(0,9);


$img = imagecreatetruecolor(120, 50);
$bgColor = imagecolorallocate($img, rand(50,150), rand(50,150), rand(50,150)); //background color - random dark coolor
$fgColor = imagecolorallocate($img, rand(200,255), rand(200,255), rand(200,255)); //foreground color - random light color
imagefill($img, 0, 0, $bgColor);

imagettftext($img, $fontSize, $angle, 25, 35, $fgColor, "./LiberationSerif-Bold.ttf", $captchaText);

setcookie("randomCharacterCookieName", $captchaText, time()+3600, '/'); // will expire in one hour

header("Cache-Control: no-cache, must-revalidate");
header('Content-type: image/png');
imagepng($img);
imagedestroy($img);

?>


Make sure your PHP has the GD library support before you proceed.

The tricky part is the one highlighted in red. You need to upload a font to your home directory to make this PHP script to work. Why don't we use the server font? Most of the time, the shared server won't have any TrueType font in it or the GD doesn't have the authority to run it. It is still better to upload your own font and you have more choice for the font as well. I chose the Liberation font as it is royalty free. You can change to your own font if you prefer.

And now comes the Javascript and HTML:

<html>

<script>

function checkCaptcha() {
 var ans = document.getElementById('answer').value;
 var tmp = document.cookie;
 var chunk = tmp.split('=');
 if (chunk[chunk.length-1] == ans) {
  alert("yes!");
  // proceed with your post verification codes such submitting the form etc.
 }
 else {
 alert("no!");
 }
}

</script>

<body>
<img src="captcha.php">
<br>
Type what you see above here:
<br>
<input type="text" id=answer size=4 maxlength=4> <a href="javascript:checkCaptcha()">Check</a>

</body>

</html>


After running the HTML, I captured this response from Chrome after a right answer is entered:



I captured this response from Chrome after entering a wrong answer purposely:



There are still many things you can improve from these codes. For example, you can still include capital letter or even some special characters to the captcha. You can also scramble the answer in the cookie and descramble it during verification with the answer embedded in the cookie.

Well, here is the Captcha tutorial! Finally!

Read More »

Tuesday, December 29, 2015

Sending Multiple MySQL Table Data from PHP to Javascript via AJAX


Note: Please run these codes from a web host, either it is a "localhost" or remote host from a web hosting server.

This is an expansion of my earlier post with sending data from only one MySQL table. For multiple table data channeling to browser from MySQL, a query string is used to differentiate the AJAX requirement. You can also create another PHP script to access data from other tables but it seems quite unnecessary as it can be easily achieved by sending different query strings to the AJAX PHP script.

Here we go again:

USE `testDB`;
DROP TABLE IF EXISTS `test`;

CREATE TABLE `test` (
 `a` tinyint(4) DEFAULT NULL,
 `b` tinyint(4) DEFAULT NULL,
 `c` tinyint(4) DEFAULT NULL,
 `d` tinyint(4) DEFAULT NULL,
 `e` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

DROP TABLE IF EXISTS `test2`;

CREATE TABLE `test2` (
 `f` tinyint(4) DEFAULT NULL,
 `g` tinyint(4) DEFAULT NULL,
 `h` tinyint(4) DEFAULT NULL,
 `i` tinyint(4) DEFAULT NULL,
 `j` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

insert into `test`(`a`,`b`,`c`,`d`,`e`) values (1,2,3,4,5),(6,7,8,9,10),(11,12,13,14,15),(16,17,18,19,20);
insert into `test2`(`f`,`g`,`h`,`i`,`j`) values (21,22,23,24,25),(26,27,28,29,30),(31,32,33,34,35),(36,37,38,39,40);


A new table 'test2' is added to the previous table setup (refer to my earlier post to check out the difference).

Here are the PHP codes for AJAX (or act as a JSON data generator):

<?php
 //I name this file ajax.php
 error_reporting(0);
 $db_name = "testDB";
 $db_server_name = "localhost";
 $db_usr_name = "xxxx"; // Please replace xxxx with your MySQL username
 $db_pw = "xxxxxxxx"; // Please replace xxxxxxxx with the password that came with it

 $dblink = mysql_connect($db_server_name, $db_usr_name, $db_pw);

 if (!$dblink) {
  array_push($error, "Failed to Connect to Database");
 }
 mysql_select_db($db_name);

 if ($_GET['tbl'] == '1') {
  $query = mysql_query("SELECT * from test");
 }
 else if ($_GET['tbl'] == '2') {
  $query = mysql_query("SELECT * from test2");
 }

 $all = array();

 $d = 0;
 while ($query_result = mysql_fetch_assoc($query)) {
  if ($_GET['tbl'] == '1') {
   $all[$d] = array("a"=>$query_result['a'],"b"=>$query_result['b'],"c"=>$query_result['c'],"d"=>$query_result['d'],"e"=>$query_result['e']);
  }
  else if ($_GET['tbl'] == '2') {
   $all[$d] = array("f"=>$query_result['f'],"g"=>$query_result['g'],"h"=>$query_result['h'],"i"=>$query_result['i'],"j"=>$query_result['j']);
  }
  $d++;
 }

 $encoded = json_encode($all);
 header('Content-type: application/json');
 exit($encoded);

?>


Finally here are the Javascript codes:

<!DOCTYPE html>
<html>

<script>

var data;

function loadJSON(path) {

 var xhr = new XMLHttpRequest();
 xhr.onreadystatechange = function() {
  if (xhr.readyState === 4) {
   if (xhr.status === 200) {
    try {
     data = JSON.parse(xhr.responseText);

     for (var k in data) {

      alert(data[k].a+" "+data[k].b+" "+data[k].c+" "+data[k].d+" "+data[k].e);


    }
    catch(e) {
     alert("Data Error. Please contact the administrator.");
    }
   }
   else {
    console.error(xhr);
   }
  }
 };
 xhr.open("GET", path, true);
 xhr.send();
}

function loadJSON2(path) {

 var xhr = new XMLHttpRequest();
 xhr.onreadystatechange = function() {
  if (xhr.readyState === 4) {
   if (xhr.status === 200) {
    try {
     data = JSON.parse(xhr.responseText);

     for (var k in data) {

      alert(data[k].f+" "+data[k].g+" "+data[k].h+" "+data[k].i+" "+data[k].j);


    }
    catch(e) {
     alert("Data Error. Please contact the administrator.");
    }
   }
   else {
    console.error(xhr);
   }
  }
 };
 xhr.open("GET", path, true);
 xhr.send();
}

loadJSON('ajax.php?tbl=1'); // This result will be the same as in the earlier post
loadJSON2('ajax.php?tbl=2'); // tell ajax.php that $_GET['tbl'] = 2;

</script>

The data from MySQL will prompt out as alerts, row by row.

</html>


Please note that the DOCTYPE declaration is important for IE browsers as it puts it into standards mode for AJAX to work.

You can also combine loadJSON with loadJSON2 by adding one more parameter to the function. Anyway, to make explanation less confusing, I added another JSON loading function to it.

After running the codes, you may get four alerts with the first time being '1 2 3 4 5' followed by '6 7 8 9 10' and so forth as in the earlier post. Then you may get the new alerts from the second table. Here is a screen shot of the first prompt from the second table running in Chrome:



Caveat: The data from the second table may prompt up before the first table. If you really want to make sure the first table come first, you will need to use the timer to delay the loadJASON2 function a bit.

Thanks for viewing!
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