When we are a variable I passed from JS to PHP it adds up

Asked

Viewed 478 times

-5

I can pass the JS variable to PHP, but when I try to add it just goes away.

<!DOCTYPE html>
<html>
<head>
    <script>
        var width = screen.width;
        var height = screen.height;
    </script>
</head>

    <?php $width = '<script>document.write(width);</script>';
    $php = $width + 10;

    echo $php;
    ?>
</body>

php javascript

2 answers

13

PHP is back-end and Javascript is front-end.

What PHP does is generate a page, it can be html, txt, image, etc., or it runs on server before reaching your browser, Javassript runs on browser.

Read these responses, although the focus is other things, I explain how the interaction works requisition and reply, recommend you read:

What the server does is send only the answer of what PHP generated to your browser, PHP has already been run and finished, so there is no way Javascript can communicate with PHP unless it is by Ajax (which is a request in "background").

When you do that:

$width = '<script>document.write(width);</script>';

You’re not passing the value of width for $width, actually PHP is seeing <script>document.write(width);</script> and not the value width.

There is no way PHP can know in the same request the value of the screen size, what you can do is use Ajax, for example:

On your page add this to your page:

<script>
(function ()
{
    function enviarTamanhoTela()
    {
        var querystring  = "largura=" + screen.width;
            querystring += "&altura=" + screen.height;

        var oReq = new XMLHttpRequest();

        //envia querystring como se fosse uma página normal
        oReq.open("GET", "atualizatamanho.php?" + querystring, true);

        //Função assíncrona que aguarda a resposta
        oReq.onreadystatechange = function()
        {
            if (oReq.readyState === 4) {
                alert(oReq.responseText); //Pega resposta do servidor
            }
        };

        //Envia a requisição, mas a resposta fica sendo aguardada em Background
        oReq.send(null);
    }

    if (/^(interactive|complete)$/i.test(document.readyState)) {
        enviarTamanhoTela();
    } else {
        document.addEventListener('DOMContentLoaded', enviarTamanhoTela);
    }
})();
</script>

And create a new file called atualizatamanho.php, you can take the data like this:

<?php

if (isset($_GET['largura'], $_GET['altura'])) {
    $largura = $_GET['largura'];
    $altura = $_GET['altura'];

    var_dump($largura, $altura); //Pode remover essa linha

    //Resto do seu código aqui
}

-6

Is that you’re trying to add a string to an integer.

try to convert the variable $width. ex. 

$width = (int) 10.9;

var_dump( $width );
  • 11

    It’s actually an issue with his code’s flux capacitor.

  • Blimey! "Code flow capacitor"... now spent

  • 11

    @Zooboomafoo code is type back to the Future, he wants the value printed by js to go back in time and run in php.

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