how does one add a + between words in a string?

[jonaofarc]

how does one add a + between words in a string? so if we have a text box and someone types john doe I would like it to come back john+doe with no spaces

[marcus]

<?php
$string = "john doe";

echo str_replace(" ","+",$string);
?>

[thebadbad]

If it's because you want to use the string as a query string part of an URL, you can urlencode() the string. That'll convert spaces to + and, and convert other 'illegal' characters.