CODEWITHSUNDEEP
javascriptphpjqueryajax
Tom
Tom

Reputation: 57

Trouble with php variables and ajax javascript

ok I have edited this to another couple of questions I've asked on a similar issue, but I really am in a rush so thought I'd start a new one, sorry if it bothers anyone.

first I have a php script on test.php on the apache server

<?php
//create connection
$con = mysqli_connect("localhost", "user", "password", "dbname");

//check connection
if (mysqli_connect_errno()){
   echo "failed to connect to MySQL: " . mysqli_connect_error();
   }
$grab = mysqli_query($con, "SELECT * FROM table");
$row = mysqli_fetch_array($grab);
$name = $row["name"];
$color = $row["color"];
$price = $row["price"];
$n1 = $name[0];
$c1 = $color[0];
$p1 = $price[0];

?>

Then I've got this ajax script set to fire onload of page a webpage written in html. so the load() function is onload of the page in the body tag. This script is in the head.

function load(){
   var xmlhttp = new XMLHttpRequest();
   xmlhttp.open("GET", "test.php", true);
   xmlhttp.send();
   xmlhttp.onreadystatecahnge = function(){
      if(xmlhttp.readyState == 4 && xmlhttp.status == 200){
         document.getElementById("itemNameLink1").innerHTML = "<?php echo $n1;?>;
         }
      }
   }

ok so what I want is the $n1 variable in the php script to be used in the javascript ajax code. Where the script is, but I'm not sure where or how to make use of the variable, I've tried a few things. All that happens right now is the innerHTML of itemNameLink1 just disappears.

I'm quite new so any advise would be appreciated, thanks.

Upvotes: 1

Views: 107

Answers (3)

George G
George G

Reputation: 7695

The response (this is what you echo in php) returned from request you can get by responseText attribute of XMLHttpRequest object. So first your JS code should be: 

function load(){
   var xmlhttp = new XMLHttpRequest();
   xmlhttp.open("GET", "test.php", true);
   xmlhttp.send();
   xmlhttp.onreadystatecahnge = function(){
      if(xmlhttp.readyState == 4 && xmlhttp.status == 200){
         document.getElementById("itemNameLink1").innerHTML = xmlhttp.responseText;
         }
      }
   }

now in php echo $n1 variable:

....
$grab = mysqli_query($con, "SELECT * FROM table");
$row = mysqli_fetch_array($grab);
$name = $row["name"];
$color = $row["color"];
$price = $row["price"];
$n1 = $name[0];
$c1 = $color[0];
$p1 = $price[0];

// echo it to be returned to the request
echo $n1;

Update to use JSON for multiple variables

so if we do this:

$name = $row["name"];
$color = $row["color"];
$price = $row["price"];

$response = array
(
    'name'  => $name,
    'color' => $color,
    'price' => $price
);

echo json_encode($response);

Then in javascript we can parse it again to have data object containing 3 variables.

var data = JSON.parse(xmlhttp.responseText);
//for debugging you can log it to console to see the result
console.log(data);
document.getElementById("itemNameLink1").innerHTML = data.name; // or xmlhttp.responseText to see the response as text

Fetching all the rows:

$row = mysqli_fetch_array($grab); // this will fetch the data only once

you need to cycle through the result-set got from database: also better for performance to use assoc instead of array

$names = $color = $price =  array();

while($row = mysqli_fetch_assoc($grab))
{
    $names[] = $row['name'];
    $color[] = $row['color'];
    $price[] = $row['price'];
}

$response = array
(
    'names' => $names,
    'color' => $color,
    'price' => $price
);

Upvotes: 1

S.Pols
S.Pols

Reputation: 3434

You should define the PHP variable. And use that variable in your javascript:

<?php
    $n1 = "asd";
?>
<html>
<head></head>
<body>

    <div id="itemNameLink1"></div>

    <script>
        function load()
        {
            var xmlhttp = new XMLHttpRequest();                     
            xmlhttp.open('GET', '/test.php', true);
            xmlhttp.send(null);
            //Note you used `onreadystatecahnge` instead of `onreadystatechange` 
            xmlhttp.onreadystatechange = function() {
                if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
                    document.getElementById("itemNameLink1").innerHTML = '<?=$n1?>';
                }
            }
        }

        load();
    </script>
</body>
</html>

Upvotes: 1

mopsyd
mopsyd

Reputation: 1922

You can dynamically generate a javascript document with php that contains server side variables declared as javascript variables, and then link this in the head of your document, and then include this into your document head whenever server side variables are needed. This will also allow you to dynamically update the variable values upon page generation, so for example if you had a nonce or something that needs to change on each page load, the correct value can be passed upon each page load. to do this, you need to do a few things. First, create a php script and declare the correct headers for it to be interpreted as a script:

jsVars.php:

<?php
//declare javascript doc type
header("Content-type: text/javascript; charset=utf-8");
//tell the request not to cache this file so updated variables will not be incorrect if they change
header('Cache-Control: no-cache, no-store, must-revalidate'); // HTTP 1.1.
header('Pragma: no-cache'); // HTTP 1.0.
header('Expires: 0'); // Proxies.

//create the javascript object
?>

var account = {
    email: <?= $n1; ?>,
    //if you need other account information, you can also add those into the object here
    username: <?= /*some username variable here for example */ ?>
}

You can repeat this for any other information you need to pass to javascript on page load, and then reference your data using the namespaced javascript object (using object namespacing will prevent collisions with other script variables that may not have been anticipated.) wherever it is needed as follows:

<script type="text/javascript>
//put this wherever you need to reference the email in your javascript, or reference it directly with account.email
var email = account.email;
</script>

You can also put a conditional statement into the head of your document so it will only load on pages where it is needed (or if any permission checks or other criteria pass as well). If you load this before your other scripting files, it will be available in all of them, provided you are using it in a higher scope than your request.

<head>

<?php
    //set the $require_user_info to true before page render when you require this info in your javascript so it only loads on pages where it is needed.
    if($require_user_info == TRUE): ?>

    <script type="text/javascript" href="http://example.com/path-to-your-script/jsVars.php" />

    <?php endif; ?>

<script type="text/javascript" href="your-other-script-files-that-normally-load" />

</head>

You can also do this for any other scripts that have to load under specific criteria from the server.

Upvotes: 1

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