Question

I’m working on a template class and I’ve an issue when trying to parse out a list of quoted strings from a string argument list. Take for example the string:

$string = 'VAR_SELECTED, \'Hello m\'lady\', "null"';

I’m having a problem coming up with a regex that extracts the string “Hello m’lady” and “null”. The closest I have got is

$string = 'VAR_SELECTED, \'Hello m\'lady\', "null", \'TE\'ST\'';
preg_match_all('/(?:[^\']|\\\\.)+|(?:[^"]|\\\\.)+/', $string, $matches);
print_r($matches);

Which outputs:

Array
(
    [0] => Array
        (
            [0] => VAR_SELECTED, 
            [1] => 'Hello m'lady', 
            [2] => "null", 
            [3] => 'TE'ST'
        )

)

However a more complex case of:

$string = 'VAR_SELECTED, \'Hello "Father"\', "Hello \'Luke\'"';
preg_match_all('/(?:[^\']|\\\\.)+|(?:[^"]|\\\\.)+/', $string, $matches);
print_r($matches);  

outputs:

Array
(
    [0] => Array
        (
            [0] => VAR_SELECTED, 
            [1] => 'Hello 
            [2] => "Father"
            [3] => ', 
            [4] => "Hello 
            [5] => 'Luke'
            [6] => "
        )

)

Can anyone help me solve this problem? Are multiple regexes the way forward?

Edit Maybe it would be easier to replace the commas within the strings with a placeholder and then break apart the strings with an explode?

Edit 2 Just thought of a simple insecure option (that I am not going to use), but generates an E_NOTICE error.

$string = 'return array(VAR_SELECTED, \'Hello , "Father"\', "Hello \'Luke\'4");';
$string = eval($string);
print_r($string);

Answer 1

Try this:

/(?<=^|[\s,])(?:(['"]).*?\1|[^\s,'"]+)(?=[\s,]|$)/

Or, as a PHP single-quoted string literal:

'/(?<=^|[\s,])(?:([\'"]).*?\1|[^\s,\'"]+)(?=[\s,]|$)/'

That regex yields the desired result, but I think you’re going about this wrong. Usually, if a quoted string needs to contain a literal quote character, the quote is escaped, either with a backslash or with another quote. You aren’t doing that, so I had to use a fragile hack based on lookarounds. Are you sure the data isn’t supposed to look like this?

$string = 'VAR_SELECTED, \'Hello m\\'lady\', "null"';

$string = 'VAR_SELECTED, \'Hello "Father"\', "Hello \\'Luke\\'"';

Come to think of it, doesn’t PHP have built-in support for CSV data?