Re: undefined variable

On 20 Feb 2014 at 12:28, Stuart Dallas <stuart@3ft9.com> wrote: > On 20 Feb 2014, at 12:25, Tim Streater <tim@clothears.org.uk> wrote: > >> and then later I do: >> >> $str = "fcc: " . $PTR_fcc; >> >> Now, upon examination it appears that I have an instance where $str ends up >> as: >> >> fcc: undefined >> >> >> My question is, under what conditions can a variable be set by the PHP system >> to the string "undefined"? Would this require that my ajax call in the >> browser would have to have had something explicit like: >> >> ... &PTR_fcc=undefined … > > Not explicit as such, but that is what’s happening. Javascript will use the > string "undefined" whenever an undefined variable is concatenated on to a > string. How about if PTR_fcc is not so much undefined on the JavaScript side, as an empty string. So that I'm passing e.g. this, via AJAX: ... &PTR_fcc=&myvar=27 ... What does that mean in my PHP script when I then do: $PTR_fcc = isset($_POST['PTR_fcc'])==true ? $_POST['PTR_fcc'] : 0; i.e. what value does $_POST['PTR_fcc'] have? -- Cheers -- Tim