Extract a substring from a string using PHP (Cake PHP application)

I need help to solve the following problem.

I have a input string as follows:-

<span class="notranslate">msgid "Default_TOP_01" </span> <br> <span class="notranslate">msgstr </span>"home <stro开发者_开发技巧ng>page </strong>" <br> <span class="notranslate">msgid "Default_TOP_02" </span> <br> <span class="notranslate">msgstr </span>"content <span>within </span>"

The desired output should be:-

msgid "Default_TOP_01" \n msgstr "home <strong>page </strong>" \n msgid "Default_TOP_02" \n msgstr "content <span>within </span>"

I need the starting and ending span tags with class="notranslate" to be removed. The <br> tags should be replaced by \n. Any tags withing the "msgstr" value should not be removed, for example msgstr "content <span>within </span>"

First run str_replace on the string to replace any occurence of <br> with \n and then strip all HTML tags from the string with strip_tags.

<?php
$str = '<span class="notranslate">msgid "Default_TOP_01" <br> <span class="notranslate">msgstr </span>"home <strong>page </strong>" <br> <span class="notranslate">msgid "Default_TOP_02" </span> <br> <span class="notranslate">msgstr </span>"content <span>within </span>"';

echo 'Original: '.$str;
echo 'Modified: '.strip_tags(str_replace('<br>', "\n", $str));                                                                                                                                                                                                                 
?>