How to Access PHP Variables in JavaScript or Jquery Rather Than ≪PHP Echo $Variable ≫

How to access PHP variables in JavaScript or jQuery rather than ?php echo $variable ?

Your example shows the most simple way of passing PHP variables to JavaScript. You can also use json_encode for more complex things like arrays:

<?php
    $simple = 'simple string';
    $complex = array('more', 'complex', 'object', array('foo', 'bar'));
?>
<script type="text/javascript">
    var simple = '<?php echo $simple; ?>';
    var complex = <?php echo json_encode($complex); ?>;
</script>

Other than that, if you really want to "interact" between PHP and JavaScript you should use Ajax.

Using cookies for this is a very unsafe and unreliable way, as they are stored clientside and therefore open for any manipulation or won't even get accepted/saved. Don't use them for this type of interaction.
jQuery.ajax is a good start IMHO.

Access PHP variable in JavaScript

You can't, you'll have to do something like

<script type="text/javascript">
   var php_var = "<?php echo $php_var; ?>";
</script>

You can also load it with AJAX

rhino is right, the snippet lacks of a type for the sake of brevity.

Also, note that if $php_var has quotes, it will break your script. You shall use addslashes, htmlentities or a custom function.

How do I pass variables and data from PHP to JavaScript?

There are actually several approaches to do this. Some require more overhead than others, and some are considered better than others.

In no particular order:

1. Use AJAX to get the data you need from the server.
2. Echo the data into the page somewhere, and use JavaScript to get the information from the DOM.
3. Echo the data directly to JavaScript.

In this post, we'll examine each of the above methods, and see the pros and cons of each, as well as how to implement them.

1. Use AJAX to get the data you need from the server

This method is considered the best, because your server side and client side scripts are completely separate.

Pros

• Better separation between layers - If tomorrow you stop using PHP, and want to move to a servlet, a REST API, or some other service, you don't have to change much of the JavaScript code.
• More readable - JavaScript is JavaScript, PHP is PHP. Without mixing the two, you get more readable code on both languages.
• Allows for asynchronous data transfer - Getting the information from PHP might be time/resources expensive. Sometimes you just don't want to wait for the information, load the page, and have the information reach whenever.
• Data is not directly found on the markup - This means that your markup is kept clean of any additional data, and only JavaScript sees it.

Cons

• Latency - AJAX creates an HTTP request, and HTTP requests are carried over network and have network latencies.
• State - Data fetched via a separate HTTP request won't include any information from the HTTP request that fetched the HTML document. You may need this information (e.g., if the HTML document is generated in response to a form submission) and, if you do, will have to transfer it across somehow. If you have ruled out embedding the data in the page (which you have if you are using this technique) then that limits you to cookies/sessions which may be subject to race conditions.

Implementation Example

With AJAX, you need two pages, one is where PHP generates the output, and the second is where JavaScript gets that output:

get-data.php

/* Do some operation here, like talk to the database, the file-session
 * The world beyond, limbo, the city of shimmers, and Canada.
 *
 * AJAX generally uses strings, but you can output JSON, HTML and XML as well.
 * It all depends on the Content-type header that you send with your AJAX
 * request. */

echo json_encode(42); // In the end, you need to echo the result.
                      // All data should be json_encode()d.

                      // You can json_encode() any value in PHP, arrays, strings,
                      //even objects.

index.php (or whatever the actual page is named like)

<!-- snip -->
<script>
    function reqListener () {
      console.log(this.responseText);
    }

    var oReq = new XMLHttpRequest(); // New request object
    oReq.onload = function() {
        // This is where you handle what to do with the response.
        // The actual data is found on this.responseText
        alert(this.responseText); // Will alert: 42
    };
    oReq.open("get", "get-data.php", true);
    //                               ^ Don't block the rest of the execution.
    //                                 Don't wait until the request finishes to
    //                                 continue.
    oReq.send();
</script>
<!-- snip -->

The above combination of the two files will alert 42 when the file finishes loading.

Some more reading material

• Using XMLHttpRequest - MDN
• XMLHttpRequest object reference - MDN
• How do I return the response from an asynchronous call?

2. Echo the data into the page somewhere, and use JavaScript to get the information from the DOM

This method is less preferable to AJAX, but it still has its advantages. It's still relatively separated between PHP and JavaScript in a sense that there is no PHP directly in the JavaScript.

Pros

• Fast - DOM operations are often quick, and you can store and access a lot of data relatively quickly.

Cons

• Potentially Unsemantic Markup - Usually, what happens is that you use some sort of <input type=hidden> to store the information, because it's easier to get the information out of inputNode.value, but doing so means that you have a meaningless element in your HTML. HTML has the <meta> element for data about the document, and HTML 5 introduces data-* attributes for data specifically for reading with JavaScript that can be associated with particular elements.
• Dirties up the Source - Data that PHP generates is outputted directly to the HTML source, meaning that you get a bigger and less focused HTML source.
• Harder to get structured data - Structured data will have to be valid HTML, otherwise you'll have to escape and convert strings yourself.
• Tightly couples PHP to your data logic - Because PHP is used in presentation, you can't separate the two cleanly.

Implementation Example

With this, the idea is to create some sort of element which will not be displayed to the user, but is visible to JavaScript.

index.php

<!-- snip -->
<div id="dom-target" style="display: none;">
    <?php
        $output = "42"; // Again, do some operation, get the output.
        echo htmlspecialchars($output); /* You have to escape because the result
                                           will not be valid HTML otherwise. */
    ?>
</div>
<script>
    var div = document.getElementById("dom-target");
    var myData = div.textContent;
</script>
<!-- snip -->

3. Echo the data directly to JavaScript

This is probably the easiest to understand.

Pros

• Very easily implemented - It takes very little to implement this, and understand.
• Does not dirty source - Variables are outputted directly to JavaScript, so the DOM is not affected.

Cons

• Tightly couples PHP to your data logic - Because PHP is used in presentation, you can't separate the two cleanly.

Implementation Example

Implementation is relatively straightforward:

<!-- snip -->
<script>
    var data = <?php echo json_encode("42", JSON_HEX_TAG); ?>; // Don't forget the extra semicolon!
</script>
<!-- snip -->

Good luck!

How to use javascript to access php variable?

Yes, you were correct.

Because PHP is executed before JavaScript, you can't change it later on, but you could do something like this:

<? $aVar = "whatever"; ?>
...
<script>
    var aVar = "<? echo $aVar; ?>"; // note the quotes! (SO's highlighter renders this incorrectly, starting a PHP block inside quotes is valid and will be recognized.)
</script>

That will send this to the client:

<script>
    var aVar = "whatever"; // note the quotes!
</script>

How to pass a PHP variable to a .JS file using JQUERY?

Echo it to HTML temaplate. If it's some structure/array use for example json format.

<script>
<?php $variable = $fetch['username']; ?>
var js_variable = <?php echo json_encode($variable); ?>
</script>

or
echo some hidden element like

<input type="hidden" id="custId" name="custId" value="<?php echo($fetch['username']); ?>">

and grab if with Jquery like

<script>
$( "#custId" ).value();
</script>

with your code
JS:

$(document).ready(function(){ var flwbtn = $(".findrowpplfollowbtn");

flwbtn.click(function(){
    var selectflwusername = $(this).parent().prev().last().find(".findpplrowusername").text();

    $.post("../php/flw.php",{$( "#custId" ).value()})

});
});

---

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