JavaScript to write and execute PHP script code to a div tag

I know php is server based and only executes when the page first loads (at run time)

my question is;
Can you use JavaScript to write and execute PHP script loaded from an external file?

this is what Ive tried;
<script type="text/javascript">
function showAreaOfTown(){
      var target = document.createElement( "script" );
      target.setAttribute( "src", "areaOfTown.php" );
      document.getElementById("areaOfTown").appendChild( target ); //the div tag
}
</script>