How to assign javascript variable in a php variable inside javascript function

[eluser]Shiju S S[/eluser]
It is not working. I tried

Code:

fcontent[j]="<?php echo $c_purpose[$i]; ?>";
"<?php $i++; ?>";
"<?php echo $i; ?>";
var x="<?php echo $i; ?>";
alert(x);

The value is just 1.