Why does my regex remove spaces?

Question

$str = "& &svnips   Â ∴ ≈ osidnviosd & sopinsdo";   
$regex = "/&[^\w;]/";
echo preg_replace($regex, "&", $str);

I am trying to replace all non-encoded ampersands with encoded ones.
The problem is that it removes the gap between &and sopinsdo.

Any idea why?

Answer 1

Why use a regex? Why not use htmlspecialchars()?

echo htmlspecialchars($str, ENT_NOQUOTES, 'UTF-8', false);

Pay attention to the fourth parameter. This means not to recode anything. Basically it will turn everything <into <, everything >into >and everything &that is not part of an existing object in&

But, if you must use a regex, you can do:

$regex = '/&([^\w;])/';
echo preg_replace($regex, '&\1', $str);

, -, ...

Answer 2

2 ( "&" NOT (; \w)) &

& ( )

Answer 3

This regex does what you are looking for.

preg_replace('/&(?!\w+;)/', '&', $text);

So, for a few simple test cases, you can get properly escaped HTML:

'& sopinsdo'          -> '& sopinsdo'
'& sopinsdo'      -> '& sopinsdo'
'sopinsdo & foo; bar' -> 'sopinsdo & foo; bar'
'sopinsdo &foo bar'   -> 'sopinsdo &foo bar'

Answer 4

This way you do not want the space between & and sopinsdo removed. Just add one

echo preg_replace($regex, "& ", $str);