Sending a message to the server and changing text on a page when a button is pressed

For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))

Scenario ...
* I wish to provide a button on my page that signals when it's pressed back to the server
* I wish the server to log the button press (a vote, perhaps) but not refresh the page
* I wish to change the text on the page to give visual feedback that the button has been pressed

Easy enough, but hard to find all in one example.

I've just added a "like" facility on to the First Great Western Coffee Shop forum.

Here's the HTML for each "like" button" (shown over multiple lines to make it easier to read):

  [<a href=/coffeeshop/lyke.php?id=154834 

  onClick='document.getElementById("txt154834").innerHTML="yum!";'>

  <span id='txt154834'>like</span></a>]

The reference number in the example is the message number that the like button is attached to; this HTML is generated by a modified PHP forum script so that the receiving lyke.php knows [i]what[/i] the user has liked. It uses the forum cookie to identify [i]who[/i] is doing the liking, and registers all likes in a MySQL database to stop users registering lots of votes for the same post.

In order to prevent the browser redrawing the page, the lyke.php includes the following header:

header("HTTP/1.1: 204 No Content");

And (as that might suggest) there is no content. the onClick Javascipt changes the work "like" into "yum!" to indicate that the button was pressed.
(written 2014-05-23, updated 2014-05-26)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles

W603 - Web and Intranet - Server Side Technologies
  [642] How similar are two words - (2006-03-11)
  [653] Easy feed! - (2006-03-21)
  [732] Where is a web site visitor browsing from - (2006-05-24)
  [1020] Parallel processing in PHP - (2007-01-03)
  [1031] robots.txt - a clue to hidden pages? - (2007-01-13)
  [1355] .php or .html extension? Morally Static Pages - (2007-09-17)
  [1365] Korn Shell scripts on the web - (2007-09-25)
  [1554] Online hotel reservations - Melksham, Wiltshire (near Bath) - (2008-02-24)
  [1615] PHP training courses every month - (2008-04-18)
  [1749] Using server side and client side programming together - (2008-08-11)
  [2055] Effect on server when memory runs out and swapping starts - (2009-02-26)
  [2282] Checking robots.txt from Python - (2009-07-12)
  [3705] Django Training Courses - UK - (2012-04-23)
  [3915] How does PHP work? - (2012-11-07)

W602 - Web and Intranet - Client Side Technologies
  [411] Javascript examples (some PHP and MySQL too) - (2005-08-13)
  [522] Javascript events - a good example - (2005-12-09)
  [1322] Flash - is it available to your web page? - (2007-08-26)
  [1681] Adding a button to a web page to print the page - (2008-06-18)
  [1812] Starting Ajax - easy example of browser calling up server data - (2008-09-27)
  [1813] Ajax - going Asyncronous and what it means - (2008-09-28)
  [1814] Javascript/HTML example, dynamic server monitor - (2008-09-28)
  [2390] Dynamic / changing images on your web page - (2009-09-01)
  [2628] An example of an injection attack using Javascript - (2010-02-08)
  [3128] How does your browser find out about itself? - (2011-01-11)
  [4310] Problem ... I want to print a series of numbered forms - (2014-10-05)

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Some other Articles

A different vision for the future
Making use of huge data, object orientation, unit testing and frameworks
Upcoming public courses from Well House Consultants
Future Swindon - Westbury train services. At current level into the future?
Sending a message to the server and changing text on a page when a button is pressed
Swindon to Weymouth - by train, the traditional way - 2014
Eurpoean Elections, and other elections ahead. Some thoughts on campaigns and policies
String formatting in Lua - string.format as a wrapper for sprintf
Dot or Colon separator between table name and member in Lua - what is the difference?
Lazy operators in Lua - what they mean, and examples

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