I want to use a PHP variable as a javascript variable - specifically I want to user the PHP variable session_id(); and use this as a javascript variable.
<?php
$php_var = session_id();
?>
<script language="JavaScript" type="text/javascript">
js_var = <?php echo($php_var ?>;
</script>
This seems like it should work for me but it doesnt can anyone suggest a better way?
The best method i can think of looks like this:
<?php
$php_var = session_id();
?>
<script type="text/javascript">
var js_var = <?php echo json_encode($php_var); ?>;
</script>
PHP's json_encode-function is always producing valid JavaScript, which is not ensured if you are simply outputting random values. If you decide not to use json_encode(), you should at least enclose the php-value with quotes to prevent syntax errors. Be aware of escaping!
<?php
$php_var = session_id();
?>
<script type="text/javascript">
var js_var = "<?php echo $php_var; ?>";
</script>
json_encode. That's what it's there for. Don't ever use the raw-echo version. You risk bugs and XSS security holes.
json_encode() does while serializing). The second example does not. That is why I recommend using the first technique. The second technique is only ever usable when dealing with already-escaped values or values that are impossible to cause invalid JavaScript, but it really does not make a lot of sense to use, since the first one covers all cases.That's just fine. Be sure that if the variable you're echoing is a string that you put quotes around it and escape any quotes, newlines, etc. inside it -- e.g., make sure it really gets output as a valid JavaScript string literal. Also, don't forget the var before js_var.
It seems you have opened a parenthesis in the echo call, but didn't close it.
Also, you should place a semicolon after it. You've also forgotten the quotes (as Gordon says in the comment below).
<?php
$php_var = session_id();
?>
<script language="JavaScript" type="text/javascript">
js_var = "<?php echo($php_var); ?>";
</script>
P.S.You can use less code by replacing echo with the '=' character:
js_var="<?=$php_var?>";
It doesn't work because your snippet contains errors, it should be:
<?php
$php_var = session_id();
?>
<script language="JavaScript" type="text/javascript">
js_var = <?php echo $php_var ?>;
</script>
