PHP JAVASCRIPT parameters passing -

i have code in php page

<?php $a = 1; <script> var foo<?php echo $a?> //var foo1 created </script> ?> 

but want separate javascipt page , pass parameter

<?php  // scripts here...  <script src="initialize.js"></script> <script> $(document).ready(function(){         initialize(<?php echo $a?>);     }); </script> 

javascript page / initialize.js

initialize(a){  var foo+a } // wanted create var foo1 

but console error cannot initialize foo+a variable

what want attain create javascript var foo1 this

thank you

<?php     $a = 1;     echo "<script> var foo".$a.";</script>" ?> 

or inside html

<?php $a = 1; ?> <script> var foo<?php echo $a?>; </script>