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iwato

Execute a $_GET Request without Page Reload

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NOTE:  The rooster has come home to rest.

BACKGROUND:  My recent ventures in SESSION variables and AJAX calls has opened up whole new worlds in the life of this unaspiring, inspired web developer.  So, far I have used each to satisfy different, but similar tasks -- namely, fill differently the same section of my podcast host page with data from the same data base using both external ($_GET and $_SESSION variables) and internal $.ajax( ) triggers.  It is now time to combine the results of these two procedures in the achievement of a third task.

At the top of my podcast host page is a PHP if-statement that checks for the receipt of two $_GET variables.  It cares not about the source of these variables and performs the same way whether they are received from an external HTTP request using a fully specified URL or my newly acquired knowledge of the href='?..." query specification.  Both cause the page load.  Neither method cares whether the page has already been loaded or not. 

QUESTION:  How do I suppress the reload function of a HTTP request without sacrificing the other features commonly associated with HTTP requests.

BY WAY OF ILLUSTRATION:  In the event that more clarity is required.

1) EXTERNAL REQUEST: 

Click on the following link:  http://www.grammarcaptive.com/podcast_dev_copy.php?hash=30a6836a3f7c5fc57751a61098e5c221&podcast_no=21

View the center section of the page that opens.  The contents of this section is inserted using a PHP script located at the top of the opened page.   The difference between a normal loading and what you observe when you click the above link can be easily seen by by omitting the query string -- namely,  http://www.grammarcaptive.com/podcast_dev_copy.php.

2) INTERNAL REQUEST:

What I would like to do is open similarly generated content using different data, from the same page.  To observe this please do the following:

Click on the word Chronology in the navigation bar of the opened page.

Click on the phrase Podcast Index ...

Click on any of phrase that reads Discover more ...

Click on the phrase Click and Listen.

Look at the result and you will discover similarly formatted, but different content in the center section of the page.  I would like to achieve the same without having to reload the page.

Could this be achieved with an event object such as 

event.preventDefault()

PLEASE ADVISE.

Roddy  :wub:

 

 

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If you want to send a request without the entire page reloading that's what ajax is for - use Javascript to send the request in the background and handle the response however you want without the current page reloading (unless you specifically reload the page for some reason).

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My very modest, current use and understanding of AJAX suggests that I would have to make the AJAX request to a page different from the page from which the AJAX request is made.  Am I wrong in this regard?

Roddy

Edited by iwato

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You can use any valid URL for an ajax request, just like with any other request.  I don't think it makes a lot of sense to send an ajax request to the current page though, if that's necessary it sounds like the code is structured in a confusing way.

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Unorthodox programming and confused programming are not the same.  Now, orthodox programming may be more efficient or easier to manipulate, but it, too, can be confusing to those who have not been reared in schooled orthodoxy.

Does there exist in Javascript an equivalent to PHP's magic  __FILE__ constant?

Roddy  B)

Edited by iwato

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I'm not talking about orthodoxy, I'm saying that it makes a lot more sense if you have a page that is dedicated to handling ajax requests only.  That seems like it would be a lot easier to maintain, and also to debug any problems without worrying about which part of the code is actually running.  Separation of concerns should be a goal for any programmer.  The best code is code that is easy to read and understand.  Having one big page which might do one of five different things doesn't help that goal.  In our major application here, there is a single ajax endpoint for all requests.  That page is responsible for doing all of the pre-processing and post-processing that happens with every single request, that code is all in one place.  Then, based on the data that was passed, it includes one of several hundred include files to do the actual processing for that particular request.  If there's a bug with a particular request we only have to pull up the include file for that request, and the only code it contains is the code which is actually for that request and not all of the general ajax handling code.  If there's a bug in the ajax code in general then we would see that with every request and it's easy to track down also.  It's not a question of orthodoxy, it's a question of organizing your code so it makes sense.

The __FILE__ constant in PHP gets the local filesystem path to the current script, that does not apply in Javascript.  If you want to get the current URL, look at the window.location object.

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I am still very new to AJAX and would like to return to this statement.

On 10/24/2017 at 2:45 PM, justsomeguy said:

If you want to send a request without the entire page reloading that's what ajax is for - use Javascript to send the request in the background and handle the response however you want without the current page reloading (unless you specifically reload the page for some reason).

and provide this as my outcome:  http://www.grammarcaptive.com/podcast_dev_copy.php.  After you have opened to the page, please follow the following steps:

  • Click on the word Chronology in the navigation bar of the opened page.
  • Click on the phrase Podcast Index ...
  • Click on any of phrase that reads Discover more ...
  • Click on the phrase Click and Listen.

What I have verified as properly functioning are the following:

  1. The creation of the data_json string containing the appropriate hash and podcast_no values.
  2. The creation of the template, if indeed, podcast.php receives the appropriate hash and podcast_no values contained in data_json.  In fact, however, I do not know whether podcast.php is receiving the data contained in the AJAX data setting.
  3. $("#main").html(template);  less template.

The following code is what produces the failure.

$('.podcast_link').find('a').on('click', function(event){
	event.preventDefault();
//	var attribute = $(this).attr('href');
	var query_str = window.location.search.replace('?', '');											
	var pairs = query_str.split('&');
	var data = [];
	$.each(pairs, function(i, v){
		var pair = v.split('=');
		var key = pair[0];
		var value = pair[1];
		var data_arr = [key, value];
		data.push(data_arr);
	});
	var data_json = JSON.stringify(data);
	var nested_ajax = $.ajax({
		url: '_utilities/php/podcast.php',
		method: 'GET',
		data: { data_json },
		dataType: 'html',
		statusCode: {
			404: function() {
			alert( "Page not found" );
		}},
		success: function(template) {
			$("#main").html(template);
		}
	});											
});

 I am concerned that the event.preventDefault statement is on steroids and is interfering with the AJAX. 

Please advise.

Roddy

p.s.  My Javascript console offers no complaint.

Edited by iwato

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In fact, however, I do not know whether podcast.php is receiving the data contained in the AJAX data setting.

That's easy enough to verify.  Set up PHP to use an error log, and you can use the error_log function to write anything you want to it.  You can make those changes at runtime, although I prefer to set these options in php.ini.

ini_set('log_errors', 1);
	ini_set('error_log', __DIR__ . DIRECTORY_SEPARATOR . 'error.log');
	error_reporting(E_ALL);

Just make sure that PHP has write access to that error.log file, it will be in the same directory as your PHP script.  Then you can use error_log to write whatever data you want to the error log.

error_log('$_GET: ' . print_r($_GET, true);
	error_log('$_POST: ' . print_r($_POST, true));

 

If I use my browser's developer tools I can see that it sends a request to http://www.grammarcaptive.com/_utilities/php/podcast.php?data_json=[[""%2Cnull]]

That %2C would be a comma, so data_json is an array that contains another array which contains an empty string and null.  Your query_str variable is an empty string because window.location is http://www.grammarcaptive.com/podcast_dev_copy.php, window.location.search is empty.  So pair is an array with 1 element (an empty string), pair[0] is an empty string, and pair[1] is null because it doesn't exist.

This doesn't have anything to do with event.preventDefault, that has specific behavior that has nothing to do with ajax.

  • Thanks 1

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Thank you for the great introduction to error logging.  I will set up in very short order.

In the meantime, I have discovered something very important about $.ajax( ) data property.  Although you can pass values to the property-value pairs of the data object via Javascript variables, you cannot do the same with the property names.  Each property name must be entered manually as a string.

Yes, it turns out that you were right both about the event.preventDefault method and the poorly specified data string.  This latter problem has been fixed and this leg of the project nearly completed.  You can see the result at podcast_dev_copy.php.  Only the animation and formatting requires further adjustment.  The actual act of podcasting will begin soon!

Today Grammar Captive celebrates the end of its 1st year of development.

Thank you all!  Especially, Dsonek, JSG, and the furtive fox.

Roddy :rolleyes:

Edited by iwato

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