Sanitize or validate Salt value as a PHP string for radioactivity-bootstrap.cfg.inc

I'm going through the Radioactivity setup process and noted that the Salt form value on the settings page may need to be sanitized or validated as a PHP string (no quotes, etc)... For example, the following salt key:

!d'pX:&y"D]y#v+d'pX:&y"D]y#v+/"D]y#v&yy#v+"D]y#vy#v+D]y#v+/

contains single quotes, which appear to break the resulting PHP code for the radioactivity-bootstrap.cfg.inc file (see attached image). I'm not able right now to test variations of characters that may break the PHP code, but I have to imagine that this field should be restricted to not use certain special characters, such that the resulting .inc file follows PHP syntax rules.