PHP regular expression match text not within strings - php

Question

I have content like foo == 'bar test baz' and test.asd = "buz foo". I need to match the "identifiers", the ones on the left that are not within double/single quotes. This is what I have now:
preg_replace_callback('#([a-zA-Z\\.]+)#', function($matches) {
var_dump($matches);
}, $subject);
It now matches even those within strings. How would I write one that does not match the string ones?
Another example: foo == 5 AND bar != 'buz' OR fuz == 'foo bar fuz luz'. So in essence, match a-zA-Z that are not inside strings.

Answer 1

/^[^'"=]*/
would work on your examples. It matches any number of characters (starting at the start of the string) that are neither quotes nor equals signs.
/^[^'"=\s]*/
additionally avoids matching whitespace which may or may not be what you need.
Edit:
You're asking how to match letters (and possibly dots?) outside of quoted sections anywhere in the text. This is more complicated. A regex that can correctly identify whether it's currently outside of a quoted string (by making sure that the number of quotes, excluding escaped quotes and nested quotes, is even) looks like this as a PHP regex:
'/(?:
(?= # Assert even number of (relevant) single quotes, looking ahead:
(?:
(?:\\\\.|"(?:\\\\.|[^"\\\\])*"|[^\\\\\'"])*
\'
(?:\\\\.|"(?:\\\\.|[^"\'\\\\])*"|[^\\\\\'])*
\'
)*
(?:\\\\.|"(?:\\\\.|[^"\\\\])*"|[^\\\\\'])*
$
)
(?= # Assert even number of (relevant) double quotes, looking ahead:
(?:
(?:\\\\.|\'(?:\\\\.|[^\'\\\\])*\'|[^\\\\\'"])*
"
(?:\\\\.|\'(?:\\\\.|[^\'"\\\\])*\'|[^\\\\"])*
"
)*
(?:\\\\.|\'(?:\\\\.|[^\'\\\\])*\'|[^\\\\"])*
$
)
([A-Za-z.]+) # Match ASCII letters/dots
)+/x'
An explanation can be found here. But probably a regex isn't the right tool for this.

Answer 2

You could also try this:
preg_match_all('/[\w.]+(?=(?:[^\'"]|[\'"][^\'"]*["\'])*$)/', $subject, $result, PREG_PATTERN_ORDER);
for ($i = 0; $i < count($result[0]); $i++) {
# Matched text = $result[0][$i];
}
To match all letters, digits and _ and dots outside your quotes. You can extend your allowable characters by adding them into [\w.]

Answer 3

The trick I use here is to force the regex to branch whenever it encounters a quote, then later on we ignore this branch.
$subject = <<<END
foo == 'bar test baz' and test.asd = "buz foo"
foo == 5 AND bar != 'buz' OR fuz == 'foo bar fuz luz'
END;
$regexp = '/(?:["\'][^"\']+["\']|([a-zA-Z\\.]+\b))/';
preg_replace_callback($regexp, function($matches) {;
if( count($matches) >= 2 ) {
print trim($matches[1]).' ';
}
}, $subject);
// Output: 'foo and test.asd foo AND bar OR fuz '
The main part of the regexp is
(?: anything between quotes | any word consisting of a-zA-Z )