I think we're using different definitions for "end of string". In PHP, the following is considered true: > var_dump(preg_match("/^[a-z0-9 ]+\$/", "hello\n"));

I think we're using different definitions for "end of string". In PHP, the following is considered true: > var_dump(preg_match("/^[a-z0-9 ]+\$/", "hello\n")); That is clear proof that "$" does NOT just match the end of the string; it also accepts an extra newline at the end of the string. In PHP you need to use \z if you want to match the end of the string, or use the "D" flag when using "$". That definition of "$" is often reasonable when you read files a line-at-a-time from a file, which is why Perl changed its definition. However, PHP is often used for server-side web applications. In this case, you are often NOT reading a line-at-a-time from a file. In such cases, allowing an extra newline at the end could be disastrous. The MediaWiki code (written in PHP) deals with this by adding the "D" flag when it uses "$", but I'm not sure it always uses it, and I doubt all PHP programs use this flag when they should.