<?php
$regex1 = '/^(|(\[[^\]]*\])|([A-Z][A-Z0-9_\-]*\s*=(\s*(("[^"]*")|(_QQ_)))+))\s*(;.*)?$/';
$regex2 = '/^(|(\[[^\]]*\])|([A-Z][A-Z0-9_\-]*\s*=(\s*(("(\"|[^"])*")|(_QQ_)))+))\s*(;.*)?$/';
$line1 = 'JLIB_LOGIN_AUTHENTICATE="Username and password do not match or you do not have an account yet."';
$line2 = 'JLIB_LOGIN_AUTHENTICATE="foo \" bar"; baz';

echo preg_match($regex1, $line1) . "\n";
echo preg_match($regex1, $line2) . "\n";
echo preg_match($regex2, $line1) . "\n";
echo preg_match($regex2, $line2) . "\n";
?>