Echo PHP variable from JavaScript?
Question
I have a PHP page with some JavaScript code also, but this JavaScript code below doesn't seem to work, or maybe I'm way off!
I am trying something like this:
var areaOption=document.getElementById("<?php echo @$_POST['annonsera_name']?>");
areaOption.selected=true;
Also I have tried this, but it only alerts a BLANK alert-box:
alert (<?php echo $test;?>); // I have tried this with quotes, double-quotes, etc... no luck
Am I thinking completely wrong here?
UPDATE
Some PHP code:
<?php
$test = "Hello World!";
?>
6 answers
solution1
10 ACCPTED 2010-01-04 09:42:44
In your second example, you are missing quotes around the string (so H is interpreted as a variable - which you didn't set).
Test this:
alert (<?php echo "'H'";?>);
OR
alert ('<?php echo "H";?>');
solution2
5 2010-01-04 10:00:26
PHP runs on the server side and Javascript is running on the client side.
The process is that PHP generates the Javascript that will be executed on the client side.
You should be able to check the JS that is generated just looking at the code. Of course, if the JS relies on some PHP variables, they need to be instanciated before the JS is output.
<?php
$test = 'Hello world';
?>
<html>
<body>
<script>
alert('<?php echo $test; ?>');
</script>
</body>
</html>
will work but
<html>
<body>
<script>
alert('<?php echo $test; ?>');
</script>
</body>
</html>
<?php
$test = 'Hello world';
?>
will not
solution3
4 2010-01-04 11:09:41
Use json_encode to convert some text (or any other datatype) to a JavaScript literal. Don't just put quotes around the echoed string — what if the string has a quote in it, or a newline, or backslash? Best case your code fails, worst case you've got a big old cross-site-scripting security hole.
So,
<?php
function js($o) {
echo json_encode($o, JSON_HEX_TAG|JSON_HEX_APOS|JSON_HEX_QUOT|JSON_HEX_AMP);
}
?>
<script type="text/javascript">
var areaOption= document.getElementById(<?php js($_POST['annonsera_name']); ?>);
areaOption.selected= true;
alert (<?php js('Hello World'); ?>);
</script>
solution4
0 2010-01-04 09:45:17
Your using @$_POST indicates that you have received (or are expecting) errors - check your generated source to see if the value was output correctly. Otherwise document.getElementById will fail and you'd get no output.
solution5
0 2010-01-04 09:45:49
alert("Delete entry <? echo $row['id']; ?> ")
solution6
0 2010-01-04 10:01:22
If your extension is js, php will not work in that file.
The reason being, php parses on files that it is supposed to. The file types that php will parse are configured in httpd.conf using AddType commands (or directives, whatever they are called).
So you have 3 options:
- add filetype js to the list of files php will parse (BAD, VERY BAD)
- make the script inline to some php file
rename the file to script.js.php, and at the beginning of the file, specify the content type, like so:
<?php header( 'content-type: text/javascript' ); ?>
Cheers!
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