什么是PHP中的这个Javascript正则表达式的等价物？

I have this js regexp which I need in PHP code now instead:

var alphaExp = /^[a-zA-ZåäöÅÄÖ\s\-]+$/;
if (!fld.value.match(alphaExp)) {
  //ERROR OUTPUT HERE
}

Whats the equivalent to this in PHP?

$string = "åäöÅÄÖ";
$alphaExp = "/^[a-zA-ZåäöÅÄÖ\s\-]+$/";
if(!preg_match($alphaExp, $string)) {
  //ERROR OUTPUT HERE
  echo "ERROR";
}