<?php
$input='foo/bar#baz';
$array = array("#" => "_", "/" => "-");
$output = preg_replace('@([a-z][#/])@e', "'<span>'.strtr('$0', $array).'</span>'", $input);
var_dump($output);
?>

Parse error: syntax error, unexpected ')', expecting '(' in /t.php(4) : regexp code on line 1

Fatal error: preg_replace(): Failed evaluating code: 
'<span>'.strtr('o/', Array).'</span>' in /t.php on line 4