Id like to count all divs with class 'count' then id like to span each divs nr

PHP Code:
<div class="count">
<
span class="count_nr"XX</span>
</
div>
<
div class="count">
<
span class="count_nr"XX</span>
</
div>
<
div class="count">
<
span class="count_nr"XX</span>
</
div>
<
div class="count">
<
span class="count_nr"XX</span>
</
div