how to access php variables from javascript code example

Example 1: javascript access php variable

//passing PHP variable to JavaScript
var myJSVar = <?php echo json_encode($myPHPVar); ?>;

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 get a variable from php to javascript

<script type="text/javascript">
// boolean outputs "" if false, "1" if true
var bool = "<?php echo $bool ?>"; 

// numeric value, both with and without quotes
var num = <?php echo $num ?>; // 7
var str_num = "<?php echo $num ?>"; // "7" (a string)

var str = "<?php echo $str ?>"; // "A string here"
</script>

Example 4: how to use php variable in javascript file

<?php
    $color = "Red";
?>
<script type="text/javascript">var color = "<?= $color ?>";</script>
<script type="text/javascript" src="file.js"></script>

Example 5: how to use php variable in javascript file

alert("color: " + color);