Código PHP:
<?php
include ("texto1.txt");
include ("texto2.txt");
include ("texto3.txt");
include ("texto4.txt");
$textscript1 = $texto1;
$textscript2 = $texto2;
$textscript3 = $texto3;
$textscript4 = $texto4;
?>
<script language="javascript" type="text/javascript">
var textos = new Array();
textos[0] = '<b>'+<? echo $textscript1; ?>+'</b>';
textos[1] = '<b>'+<? echo $textscript2; ?>+'</b>';
textos[2] = '<b>'+<? echo $textscript3; ?>+'</b>';
textos[3] = '<b>'+<? echo $textscript4; ?>+'</b>';
var indice = 0;
</script>