Integrating Javascript Return Value

JessePHP

Hey all,

I've come across quite a hurdle... and want to get some suggestions on how it should be tackled. Let me lay it out for you all...

I have a PHP function which loops through a MySQL result set. I have also developed a javascript function which uses the Google Maps API to get the distance in metres of two given addresses:

<script type="text/javascript">

function getLength(from, to) {
	geocoder = new GClientGeocoder();

	geocoder.getLatLng(from,function(from_gl) {
		if (!from_gl) {
			//alert(from + " not found");
			Set_Cookie('bookmein_distance', result, 1, '/', '', '');
		}
		else {
			geocoder.getLatLng(to,function(to_gl) {
				if (!to_gl) {
					//alert(to + " not found");
					Set_Cookie('bookmein_distance', result, 1, '/', '', '');
				}
				else {
					//alert ("Both addresses were found!");
					result = (to_gl.distanceFrom(from_gl));
					//alert(result);
					//document.getElementById("main").innerHTML = result;
					//return (result);
					Set_Cookie('bookmein_distance', result, 1, '/', '', '');
					//document.write(result);
				}
			});
		}
	});
}

window.onload=function(){
	getLength("<?php echo $_GET["from"]; ?>","<?php echo $_GET["to"]; ?>");
	//myResult = getLength("<?php echo $_GET["from"]; ?>","<?php echo $_GET["to"]; ?>");
	//alert (myResult);
	//Set_Cookie('distance_result', myResult, 1, '/', '', '');
}

function Set_Cookie( name, value, expires, path, domain, secure ) {
	// set time, it's in milliseconds
	var today = new Date();
	today.setTime( today.getTime() );

	/*
	if the expires variable is set, make the correct
	expires time, the current script below will set
	it for x number of days, to make it for hours,
	delete * 24, for minutes, delete * 60 * 24
	*/
	if ( expires )
	{
	expires = expires * 1000 * 60 * 60 * 24;
	}
	var expires_date = new Date( today.getTime() + (expires) );

	document.cookie = name + "=" +escape (value) +
	( ( expires ) ? ";expires=" + expires_date.toGMTString() : "" ) +
	( ( path ) ? ";path=" + path : "" ) +
	( ( domain ) ? ";domain=" + domain : "" ) +
	( ( secure ) ? ";secure" : "" );
}

Now, the problem is that on each iteration of results from the MySQL query, I want to call this javascript function using addresses returned from the query, have the javascript value passed to a php variable and use it as I would do in that function. And to answer the obvious question, it doesn't seem there is a PHP equivalent API to google maps...

I've moved the javascript function to a separate page, as you'll see in the code, the function is called onload, with PHP to take the from/to from the URL. Opening the page on it's own - for some reason document.write()/writeln() and println() fails to put the result to screen, however I've tested that it sets the cookie just fine.

Foolishly, I thought that I could open the URL from the PHP function using fopen(), and then using $_COOKIE[...] to get the returned result, but of course this function just opens a file stream, so yeah, not that simple.

So, where to next. I've found http://satoewarna.com/jqsajax/, but don't want to go to such lengths just to make this functional... Would like to ask - has anyone used the function http_get(), and by doing so does it invoke the URL's javascript?

Thanks all,
Jess.

sneakyimp

If you call a PHP script which has an onload function that gets google API data and then writes it to a cookie, then those cookies are not going to exist until after PHP has completely finished rendering the page.

Surely there is some way to interface with the google API other than using javascript. Perhaps you should read this thread which describes interfacing with the google api using [man]cURL[/man]. This page describes using PHP and cURL to interface with google.

If you have many lookups to do at once, you can use [man]curl_multi_exec[/man] to run many queries at once to have better performance.

JessePHP

Cheers Sneaky, sound suggestion.

Yeah, I used the cURL to only get the coordinate's which is successful, but I'm quite a newb using cURL functions let alone the curl_multi_exec... So then I discovered I could do it in the following way:

function getCoords($address) {
	// Initialize Variables
	$key = "";
	$url = "";
	$handle = "";
	$source = "";

$key = "...";
$url = "http://maps.google.com/maps/geo?q=".$address."&output=csv&key=".$key;
$handle = @fopen($url,'r');
Do {
	sleep(1);
	$source = fread($handle,250);
} while ( $source = "" );
fclose($handle);
//echo $source;
$arrCoords = split(",",$source);
return '###'.$arrCoords[2].'###'.$arrCoords[3];
}

This appends the coords to the string array containing results, I then have those results echo'd to a javascript to calculate the distance:

function distance(lat1, lon1, lat2, lon2, unit) {
	var radlat1 = Math.PI * lat1/180
	var radlat2 = Math.PI * lat2/180
	var radlon1 = Math.PI * lon1/180
	var radlon2 = Math.PI * lon2/180
	var theta = lon1-lon2
	var radtheta = Math.PI * theta/180
	var dist = Math.sin(radlat1) * Math.sin(radlat2) + Math.cos(radlat1) * Math.cos(radlat2) * Math.cos(radtheta);
	dist = Math.acos(dist)
	dist = dist * 180/Math.PI
	dist = dist * 60 * 1.1515
	if (unit=="K") { dist = dist * 1.609344 }
	if (unit=="N") { dist = dist * 0.8684 }
	return dist
}

The PHP function works heaps fast on it's own, so I didn't think I'd have any problems when I used it with a for loop going through my array of results, but it locks up the whole page and gives the fatal error of exceeding the execution timeout.

I have since added the:

Do {
sleep(1);

To try and pause between attempts, but this hasn't helped... What do you think??

Cheers,
Jess.

Kudose

See [man]set_time_limit[/man]

JessePHP

Cheers Kudose - yeah I came across this - but the issue isn't really that I want to allow the script more time to run, but rather perform it more efficiently so the default execution time is ample.

As an example, if I run the PHP function getCoords() above with one address on a test page, the result is returned and echo'd in just a second.

While if I just have one or two addresses in a array, and passed to this function to get the results appended to each array item, the script completely locks up... No idea why...

Cheers.

sneakyimp

My guess is that if you run multiple queries to the api one after the other, the network latency is going to kill your performance. That's why I suggested [man]curl_multi_exec[/man]. curl_multi_exec allows you to queue up a large number of requests all at once and cURL will execute them simultaneously rather than one after the other. The results are gathered asynchronously. I haven't used it either so I'm not sure what else to say. It might be a bit tricky but probably a lot less so than any other ways I can imagine -- unless the google API permits a batch query of some kind. Either way, you have some doc-reading and experimenting to do.

Kudose

The fatal error is due to the script taking too long to run. Adding in sleep() just makes it take longer and is worse.

You need to isolate what is taking up the time and fix it. I wouldn't use JavaScript to find the distance. I would either use the Great Circle formula in SQL or use the PHP GeoCalc class (http://www.imaginerc.com/software/GeoCalc/). GeoCalc is fast.

Looking back at your code, I think your do/while loop is the culprit and shouldn't even be used. As soon as you get the first chunk of data back, it will break the loop. No point in using it. Just increase your buffer in fread.

Just my 2 cents.

JessePHP

Hey guys,

Yeah Sneaky, more doc reading is right. I would have used the cURL for multi exec, if I knew the in's and out's of it - and that latency is killing the script. Going to have to try and learn how to use it more.........

And Kudose, yeah your right about the Sleep() thing making it worse, I just foolishly had it in my head that it would give a pause so the function a chance to get the handle to the variable, and the amount of the buffer is ample, again, was just hoping it could cycle the loop until the variable had it's data in there... it was a desperate attempt really... originally with the single test, there was no such loop or sleep() and it was heaps fast, so I had my hopes about the loop...

Anyway, as to the javascript to find the distance between to given coordinate's, I doubt very much that will be a problem with that at all - just a few math operations, and from the Great Circle, I'd still need to get the latitude and longitude first.

I'll take out the loop and try some more tests with arrays and isolated from the whole page, but if still to no avail, I'll look more in to curl_multi_exec...

How annoying, this bit is holding up progress! :-/

Cheers,
Jess

sneakyimp

I did a google for "batch geocode google" and found this:
http://onemarco.com/2007/06/03/geocoding-with-the-google-maps-api/

who knows, it may be helpful.

If you choose to do curl_multi_exec, this sample from the source code could be modified:

<?php
// create All your curl resources here...you don't need separate
// vars, just create an array instead
$ch1 = curl_init();
$ch2 = curl_init();

// set URL and other appropriate options...like POST or GET vars or whatever
// loop if you use an array
curl_setopt($ch1, CURLOPT_URL, "http://lxr.php.net/");
curl_setopt($ch1, CURLOPT_POST, TRUE);
curl_setopt($ch1, CURLOPT_POSTFIELDS, $data);

curl_setopt($ch2, CURLOPT_URL, "http://www.php.net/");
curl_setopt($ch2, CURLOPT_POST, TRUE);
curl_setopt($ch2, CURLOPT_POSTFIELDS, $data);


//create the multiple cURL handle
$mh = curl_multi_init();

//add the handles...loop if you use an array
curl_multi_add_handle($mh,$ch1);
curl_multi_add_handle($mh,$ch2);

$active = null;
//execute the handles
do {
    $mrc = curl_multi_exec($mh, $active);
} while ($mrc == CURLM_CALL_MULTI_PERFORM);

while ($active && $mrc == CURLM_OK) {
    if (curl_multi_select($mh) != -1) {
        do {
            $mrc = curl_multi_exec($mh, $active);
        } while ($mrc == CURLM_CALL_MULTI_PERFORM);
    }
}

//close the handles, loop you have an array
curl_multi_remove_handle($mh, $ch1);
curl_multi_remove_handle($mh, $ch2);

// close the multi handle
curl_multi_close($mh);

?>

JessePHP

Thanks for the help, Sneaky 🙂

The batch geocode looks pretty impressive - but it was difficult to extract what I wanted to - it seemed to be heavily dependent on the map/sidebar objects.

However, I removed the sleep()/loop from the other php script, and finally got something to output, not sure why I couldn't before, but it showed that a 400 Bad Request was being read, then I realised that the addresses I was passing in the other script I was merging it with was making the URL formatted incorrectly, so used the urlencode() and all became right.

Happy days! 😉
Cheers,
Jess.