How can i add a span element to this snippet of php

Hello,

I am trying to wrap a span html element around $bi_i in the following snippet of code:

echo str_ireplace(';', ', ', substr($i->fields[$diddy_all[$bi_i]],1,-1));

 

Here is what i have tried to do with no success:

echo str_ireplace(';', ', ', substr($i->fields[$diddy_all['<span class="'.$bi_i.'"></span>']],1,-1));

 

Thanks for looking.