Echo PHP inside Javascript?

Question

Why is this not working?

<?php 

mysqli_select_db($connect,"dev");
$response = "Select response from revbut where session='$u'";
$rquery  =  mysqli_query($connect,$response);

$responseanswer = mysqli_fetch_array($rquery);
$re  = $responseanswer['response'];
?>

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

$re inside JavaScript is not getting echoed. But if I place it inside the above PHP function, it is getting echoed.

EDIT - BUT THEN WHY IS THIS NOT WORKING?

if(<?php echo $re; ?>){
    document.getElementById('hide').style.display = "none";
}

if I PLACE the hide function outside the if - it is working.

which php function? there's no function in this code.

StasM
– StasM

2010-12-28 08:23:41 +00:00
Commented Dec 28, 2010 at 8:23 — StasM
– StasM, Commented Dec 28, 2010 at 8:23

Lee Taylor · Accepted Answer · 2024-05-10 12:07:51Z

21

It get's echoed, but you won't see anything on your page as the text will be written within the Javascript-tag which is not displayed by the browser. Look at your page source to verify that the text is really there.

EDIT

Try

if(<?php echo json_encode($re); ?>){
    document.getElementById('hide').style.display = "none"; 
}

This will ensure that your PHP string will be converted into the appropriate Javascript type - in case of strings it'll ensure that the string is enclosed in " and is escaped properly.

EDIT again

When you do the following

<script type="text/javascript"> 
if(<?php echo $re; ?>){
    document.getElementById('hide').style.display = "none"; } 
</script>

this is what is written to the HTML page (that's then interpreted by the browser)

<script type="text/javascript"> 
if(whatever is in the $re variable){
    document.getElementById('hide').style.display = "none"; } 
</script>

But this is not even valid Javascript. What you want is

<script type="text/javascript"> 
if("whatever is in the $re variable"){
    document.getElementById('hide').style.display = "none"; } 
</script>

Note the " which ensures that the whole thing is valid Javascript and that the contents of $re will be interpreted as an Javascript string by the Browser's Javascript engine. The call to json_encode() does exactly this - it transforms PHP variables into the appropriate Javascript variables.

edited May 10, 2024 at 12:07

Lee Taylor

7,99416 gold badges38 silver badges53 bronze badges

answered Dec 28, 2010 at 8:23

Stefan Gehrig

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1 Comment

sarthak Over a year ago

ONE WORD - GENIUS...THANKS.....IT IS WORKING...CAN U PLEASE EXPLAIN ME WHY THIS WORKED, IF POSSIBLE.

Umang Goyal · Accepted Answer · 2010-12-28 08:24:03Z

5

try this:

<script type="text/javascript">
alert('<?php echo $re; ?>');
</script>

answered Dec 28, 2010 at 8:24

Umang Goyal

591 bronze badge

1 Comment

li bing zhao Over a year ago

This is nice reminder, it works to echo your php variable

Álvaro González · Accepted Answer · 2010-12-28 08:38:27Z

1

First, you cannot assume that all DB related operations will always complete sucesfully and will always return data. Open the PHP manual, review all your mysqli_* function calls and add a proper test to detect whether they return an error code or not.

Second, PHP and JavaScript don't run at the same time. After PHP is done all you get is some plain text that's sent to the browser. If that text happens to be JavaScript code, it will be run. And you don't have to guess: the JavaScript code is right there and you can use your browser's View Source menu to inspect it.

answered Dec 28, 2010 at 8:38

Álvaro González

147k45 gold badges282 silver badges378 bronze badges

Comments

Community · Accepted Answer · 2013-02-01 18:06:43Z

0

do view source it is echoing try it and confirm

<script type="text/javascript">
alert('<?=$re; ?>');
</script>

edited Feb 1, 2013 at 18:06

CommunityBot

11 silver badge

answered Dec 28, 2010 at 8:23

Shakti Singh

86.7k21 gold badges142 silver badges156 bronze badges

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