使用正则表达式匹配特定模式

Question

I'm trying to match any strings that doesn't start with "false1" or "false2", and ends with true, but the regex isn't matching for some reason. What am I doing wrong?

$text = "start true";
$regex = "~(?:(^false1|false2).+?) true~";
if (preg_match($regex, $text, $match)) {

echo "true";    

}

true

null

Answer 1

You may use negative lookahead.

^(?!false[12]).*true$

If you really want to use boundaries then try this,

^(?!false[12]\b).*\btrue$

DEMO

Update:

^(?!.*false[12]\b).*\btrue$

(?!.*false[12]\\b) negative lookahead which asserts that the string would contain any char but not the sub-string false1 or false2 and it must ends with the string true , that's why we added true$ at the last.