need help replacing Str replace url with another url address

[dj30324]

ok i am ready runnng a script using someting like

http://dl1.hostname.net/stream/6fd7f25ef86cfcdd92c560ad8e7d6f3e/1245802950/61591093/SAKKU%201_chunk_1.wmv

$a = http://dl1.hostname.net/stream/6fd7f25ef86cfcdd92c560ad8e7d6f3e/1245802950/61591093/SAKKU%201_chunk_1.wmv

$a generates this link above but before it gets generated i want to replace the

$a= only part of the url from /stream/ to /download/

how would i do this is it something like this
$a= str_replace("/stream/ ", "/download/", $a);

i need help thanks questions how would i do this in to a php code
replacing above url /stream/ with /download/

in php code plz help

[techietim]

$a = str_replace('/stream/', '/download/', $a);