php regex is not escaped

Question

what is a regex to find any text that has 'abc' but does not have a '\' before it. so it should match 'jfdgabc' but not 'asd\abc'. basically so its not escaped.

Answer 1

Use:

(?<!\\)abc

This is a negative lookbehind. Basically this is saying: find me the string "abc" that is not preceded by a backslash.

The one problem with this is that if you want to allow escaping of backslashes. For example:

123\\abcdef

(ie the backslash is escaped) then it gets a little trickier.

Answer 2

$str = 'jfdg\abc';

var_dump(preg_match('#(?<!\\\)abc#', $str));

Answer 3

Try the regex:

(?<!\\)abc

It matches a abc only if its not preceded by a \