Retrieve constantly from database - php

I am doing this animation tool where I fetch a value from my database and then a picture will animate to a certain position. My question is if it is possible to retrieve data constantly or like every 5 seconds?
Somehow like this:
while(autoretreive){
$data = mysql_query("select * from ......");
}
UPDATED from here
Thanks for your answers! Made it a little bit clearer what to do! Maybe I can explain better what I'm doing in my code.
I am doing this animation program as said, where balls with information is moving around to different locations. I have one value that will be updated frequently in the database, lets call it 'city'.
First at previous page I post the balls of information I want based on the 'city' and I do like this (simplified):
$pid = $_POST['id'];
$pcity[0] = $_POST['city'];
$pcity[1] = $_POST['city'];
$pcity[2] = $_POST['city'];
//...
$while(autoretrieve) { // HOW TO?
$data = mysql_query(select * from table where city == $pcity[0] OR $pcity == [1] //...);
while($rows = mysql_fetch_array($data)){
$city = $rows['city'];
$id = $rows['id'];
if($city == example1){
"animate to certain pos"; //attached to image
}
else if($city == example2){
"animate to certain pos"; //attached to image
}
}
}
So for every update in the database the image will animate to a new position. So a time interval of 5 seconds would be great. I'm not an expert in coding so sorry for deprecated code. Not so familiar with AJAX either so what is going to be imported to the code? It is also important that the page is not reloading. Just the fetch from database.

you can do it with ajax and javascript
make one javascript function which contains ajax code to retrive data from database
and at your page load using setTimeout call your ajax function at every 5 second

You can use sleep function to control how often you want to fetch data.
while(autoretreive){
$data = mysql_query("select * from ......");
//output your data here, check more in link about server sent events bellow
sleep(5);
}
Since you haven't specified how you plan to access data I'm writing this answer assuming Server-Sent Events as they are only ones that make sense according to your question.
Now all this was according to your question which wasn't very clear on how do you plan to use data. Again you'll most likely want to fetch data using ajax, but Server Sent Events can also be a good way you could achieve this.
And don't use mysql_* it's deprecated, switch to PDO or mysqli_*

Related

PHP DB caching, without including files

I've been searching for a suitable PHP caching method for MSSQL results.
Most of the examples I can find suggest storing the results in an array, which would then get included to page. This seems great unless a request for the content was made at the same time as it being updated/rebuilt.
I was hoping to find something similar to ASP's application level variables, but far as I'm aware, PHP doesn't offer this functionality?
The problem I'm facing is I need to perform 6 queries on page to populate dropdown boxes. This happens on the vast majority of pages. It's also not an option to combine the queries. The cached data will also need to be rebuilt sporadically, when the system changes. This could be once a day, once a week or a month. Any advice will be greatly received, thanks!
You can use Redis server and phpredis PHP extension to cache results fetched from database:
$redis = new Redis();
$redis->connect('/tmp/redis.sock');
$sql = "SELECT something FROM sometable WHERE condition";
$sql_hash = md5($sql);
$redis_key = "dbcache:${sql_hash}";
$ttl = 3600; // values expire in 1 hour
if ($result = $redis->get($redis_key)) {
$result = json_decode($result, true);
} else {
$result = Db::fetchArray($sql);
$redis->setex($redis_key, $ttl, json_encode($result));
}
(Error checks skipped for clarity)

PHP isnull First pass/Second pass flag

I have a PHP results page which starts off "first-pass" with ALL rows returned. It's a search listing of all pizza places in the county.
SELECT * from pizzeria;
Then the user can drill down into more detail... the page also has a CSS dropdown menu where the user can pick a specific neighborhood (which carries a URL):
href="samepage.php?neighborhood=HELLSKITCHEN"
which then changes the query after I pick up the $_GET[]
SELECT * from pizzaria WHERE nbh=(the $_GET[] variable sent in the URL);
but I'd like the page to call itself and I have header("Cache-Control:no-cache"); at the top.
I'm trying to create a first-pass or first visit flag variable with the isnull() function:
if (is_null($firstpass)) {
$query = SELECT all the records from the pizzaria table
} else {
$query = SELECT only the records WHERE I $_GET[] the value from the reloaded URL
}
It seems though that the $firstpass variable doesn't stick on reloads. Should I SESSION that variable? (though still have the problem of constantly resetting it)
Or maybe implement some other approach?
I know I can redirect to a separate second page and javascript back to this page to avoid "headers already sent", but I want to avoid the round-trip back to the client.
Is there a known best practice on reloads with new info? Kinda new to PHP here. thanks
Maybe I didn't understand well your problem but why wouldn't you do :
if (!isset($_GET['example'])) {
$query = 'SELECT * FROM pizzerias';
} else {
$query = 'SELECT * FROM pizzerias WHERE pizzeria = \'.mysql_real_escape_string($_GET['example']).\' LIMIT 1';
}
at the first pass because, it seem that the $_GET variable is set only when the user choose a pizzeria?
Here is a more targeted answer.
NOTICE: mysql_* functions are being depreciated, so use PDO instead. In my example I'm being semi-lazy and not using PDO.
//Connect to database and define table up here
...
if(!isset($_GET['neighborhood')){
$q = "SELECT * FROM pizzeria;";
}else{
$q = sprintf("SELECT * FROM pizzeria WHERE nbh=%s",mysql_real_escape_string($_GET['neighborhood']));
}
$query = mysql_query($q);
foreach($row = mysql_fetch_array($query,MYSQL_ASSOC){
//display the updated view of restaurants.
}
I would also suggest that you use jQuery for that Web 2.0 effect. It's really nice when you select from a drop-down menu and things magically move without a page reload.

repeating php in javascript

Hi I have the following code and was wondering if its possible to make the PHP part repeat so the javascript var is kept upto date even if a new row has been add to the table?
<script type="text/javascript" >
var total_rows = [];
<?php
$con = mysql_connect("localhost", "user", "password");
$total = mysql_query("SELECT * FROM table");
$num_rows = mysql_num_rows($total);
?>
var total_rows = "<?php echo $num_rows ; ?>";
</script>
Not directly, because PHP is server side only, and has finished executing by the time your JS is executed.
While you could check it without reloading the page using AJAX, I would question whether what you are doing is useful anyway - the client should not care about the number of rows in a table as a general rule - the only real exception being if you are making a database management page, and even then it's usefulness is debatable. If you need to update/delete a row from client input, all you need is the ID of the row, and if you are adding one you should let the database generate a row ID for you with an auto-incrementing primary key.
I suspect you would be better looking at your application's implementation as whole if you have reach a point where you feel you need this information at the client side.
You can use AJAX to update parts of your page without reloading the entire page. You should look into that. A good tutorial to start will be http://www.w3schools.com/php/php_ajax_intro.asp.
Repeating the PHP code in HTML itself is not possible, because the PHP code is not available in the HTML page. The HTML page is the result of executing a PHP script.
You would need to use AJAX to hit a file which does the PHP select and returns the desired row.
You would have to refresh your query to get the latest count, so I would do something like this. this example uses jquery: http://api.jquery.com/jQuery.get/
function get_updated_rows(){
$.get('count.php', function(data) {
var total_rows = data;
})
return total_rows;
}
You count.php file would contain the php:
<?php $con = mysql_connect("localhost", "user", "password");
$total = mysql_query("SELECT * FROM table");
$num_rows = mysql_num_rows($total);
echo $num_rows;
?>
then when you need the updated count, just use your function: get_updated_rows();

i am trying to call back a string in PHP JQUERY

I am trying to call back the value of content_columns to jquery.
PHP CODE:
if($act=="getcol"){
$pid=$_GET['pid'];
$domain_id = 1;
$PAGEresult = mysql_query("SELECT * FROM pages WHERE domain_id='$domain_id' AND id='$pid' ORDER BY id DESC");
$PAGErow = mysql_fetch_array($PAGEresult);
echo json_encode($PAGErow['content_columns']);
}
jQuery
$.get("get_actions.php?act=getcol&pid="+pid, function(data){
alert(data);
});
Can someone lead me down the right path please.
If by "same string" it is possible that it is cached. You can disable caching with jQuery's ajax library that you are using. You can also send a different query string such as with the system time to ensure you don't get a cached results. You can also use POST.
You will only ever get one result from that query. If you want multiple results, you need to iterate over mysql_fetch(). If you only want one result, add LIMIT 1 to your query. Otherwise it is incredibly wasteful. Finally, why use SELECT *? Use SELECT content_columns ..

How to periodically push data to the user interface in php

i need to implement a simple project using PHP and MySql in which i need to push data to the user's UI when some one else is updating the database, and i need to periodically do this too, so when some one else accessing the same table and modify it, another person who uses the UI can see the updates, sorry if i'm being silly but up to now i'm only aware of saving data to a database and retrieving and showing it to the user(simplest form of data base connection). how can i achieve this in php, please some one help me on this matter, if the answer explains the things in detail it is good, because i'm very novice to this.thanks in advance.
rangana.
If the web page has no data to return, then get the page to wait for a period while polling the database. You must use the sleep statement to avoid maxing out your server.
Warning: Some servers wont let the user open another page while one is in progress, which may cause you problems in some situations. So either dont hold the page open for too long, or maybe try to get the ajax page to use a different session.
// do this when you have put new data in to database
setappdata("lastupdate",microtime(true));
// use this loop to poll for new data
$loop = 0;
$lastupdate=$_SESSION["lastupdate"];
while ($lastupdate==$last=getappdata("lastupdate") and $loop<10) {
$loop++;
usleep(500000); //0.5sec
}
// use a table called appdata to store application data
function getappdata($var) {
$query = "SELECT data FROM appdata WHERE var='$var'";
$res1=mysql_query($query);
if (mysql_numrows($res1)<1) return false;
return mysql_result($res1,0,"data");
}
function setappdata($var,$data) {
$query = "SELECT data FROM appdata WHERE var='$var'";
$res1=mysql_query($query);
if (mysql_numrows($res1)>0) $query = "UPDATE appdata SET data='$data' WHERE var='$var'";
else $query = "INSERT INTO appdata SET var='$var',data='$data'";
return mysql_query($query);
}
These topics may get you started:
http://en.wikipedia.org/wiki/Push_technology
http://en.wikipedia.org/wiki/Reverse_Ajax

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