How do I strip all spaces out of a string in PHP?

Do you just mean spaces or all whitespace?

For just spaces, use str_replace:

$string = str_replace(' ', '', $string);

For all whitespace (including tabs and line ends), use preg_replace:

$string = preg_replace('/\s+/', '', $string);

(From here).

If you know the white space is only due to spaces, you can use:

$string = str_replace(' ','',$string); 

But if it could be due to space, tab...you can use:

$string = preg_replace('/\s+/','',$string);

If you want to remove all whitespace:

$str = preg_replace('/\s+/', '', $str);

See the 5th example on the preg_replace documentation. (Note I originally copied that here.)

Edit: commenters pointed out, and are correct, that str_replace is better than preg_replace if you really just want to remove the space character. The reason to use preg_replace would be to remove all whitespace (including tabs, etc.).

str_replace will do the trick thusly

$new_str = str_replace(' ', '', $old_str);