How to use preg_replace outside <script></script> in php

Question

I've got a string :

$source = '&
<script type="text/javascript">&</script>
&
<script type="text/javascript">&</script>
&';

The desired result is :

&
<script type="text/javascript">&</script>
&amp;
<script type="text/javascript">&</script>
&amp;

I try with :

echo preg_replace("#&(?!amp;)(?!<\/script>)(?![^<]script.*?>)#i",
                  "&amp;", $source);

But I can only replace the first "&" or they are all replaced.

How can I get this result ?

Edit 1 :

Now if I've got a string :

$source = '&
<script type="text/javascript">text&text</script>
&
<script type="text/javascript">&</script>
&';

The desired result is :

&
<script type="text/javascript">text&text</script>
&amp;
<script type="text/javascript">&</script>
&amp;

Answer 1

Using the g modifier replaces your match globally (every occurence).

echo preg_replace("#&(?!amp;)(?!<\/script>)(?![^<]script.*?>)#ig",
                  "&amp;", $source);

Answer 2

Try this

$output = preg_replace("/&(?!amp;)(?!<\/script>)(?![^<]script.*?>)/", "&amp;", $source);

Answer 3

Stop it with the regexes already. Please. I can't take it anymore. My head hurts, but only because I'm banging it on my desk.

I would suggest using DOMDocument or SimpleXmlElement to parse the string and then loop through each non-script tag to encode each ampersand.