@sparker, I think it's fair to assume he's talking about PHP here, give that he posted the question in the PHP forum.
To answer the question: in PHP, simple string replacement can be done using the str_replace() function. Note that $search
and $replace
parameters (first and second, respectively) for the function can take arrays, so if you wanted to replace all of the three items you mentioned, you could put them in an array and pass that as the first parameter, and then pass the space character as the second parameter.
If a more complicated replacement is needed, PHP's regular expression replacement function, preg_replace(), can be used instead.
If I recall (i am sorry if i am wrong) but you can use   to create a space (as far as i am aware of, this works in html to create a single space).
The  
entity should indeed create a space, but a "thin" space, which is shorter than a normal space. How short would depend on the browser, but it could be significantly shorter.
A standard space can be added in HTML using the
entity. I'd recommend that instead, since its' more or less "the" space entity in HTML, supported in every browser ever made. (Support for  
isn't as widespread.)