How to pass array index value in string using php?

Question

I want to write and pass array index value in string to another php file. Kindly check what I am doing:

<?php
$pages = array("Story1","Story2","Story3");
$fp = fopen('urls.php', 'w');
for($i=0;$i<$length;$i++){
fwrite($fp, '<a href="kids-{$pages[$i]}">Kids App Stories</a><br>');
}
fclose($fp);
?>

I am having problem below line:

fwrite($fp, '<a href="kids-{$pages[$i]}">Kids Stories</a><br>');

The above line write as it is in urls.php

<a href="kids-**{$pages[$i]}**">Kids Stories</a><br>
<a href="kids-**{$pages[$i]}**">Kids Stories</a><br>
<a href="kids-**{$pages[$i]}**">Kids Stories</a><br>

While I am expecting the output:

<a href="kids-story1">Kids Stories</a><br>
<a href="kids-story2">Kids Stories</a><br>
<a href="kids-story3">Kids Stories</a><br>

I want in urls story1,story2,story3 instead of {$pages[$i]}

Any idea or suggestions would be welcome.