PHP variable to Javascript variable:
<?php $myvar=10; ?>
<script type="text/javascript">
jsvar = <?php echo $myvar; ?>;
document.write(jsvar); // Test to see if its prints 10:
</script>
Form variable to Javascript variable:
<form name="myform4">
<input type="hidden" name="formvar" value="100">
</form>
<script type="text/javascript">
jsvar = document.myform4.formvar.value;
document.write(jsvar) // test
</script>
PHP variable to Form variable:
<form name="myform4">
<input type="hidden" name="formvar" value="<?php $phpvar=10; echo $phpvar; ?>"> // PHP code inside HTML!!
</form>
Javascript variable to Form variable:
<form name="myform3">
<!-- It needn't be a "hidden" type, but anything from radio buttons to check boxes -->
<input type="hidden" name="formvar" value="">
</form>
<script type="text/javascript">
jsvar=10;
document.myform3.formvar.value = jsvar;
</script>