how to use javascript variable in php code example

Example 1: javascript php variable

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

Example 2: using js variable in php

<script type="text/javascript">
var abc= 'this is text';
<?php $abc = "<script>document.write(abc)</script>"?>   
</script>
<?php echo $abc;?>

Example 3: how to use javascript variable in php

<script>
var p1 = "success";
</script>

<?php
echo "<script>document.writeln(p1);</script>";
?>

Example 4: how to use php variable in javascript file

<?php
$bool = false;
$num = 3 + 4;
$str = "A string here";
?>

Example 5: how to use php variable in javascript file

alert("color: " + color);