php preg_replace没有像预期的那样工作

I've got the following code:

<?php
    $test = "xxxx..AAA?!";
    echo $test."
";
    $test = preg_replace("[^a-zA-Z0-9-]", "", $test);
    echo $test."
";
?>

I want to delete all chars which aren't letters, numbers or a minus

What's my mistake?

delimiter is missing

$test = preg_replace('/[^a-zA-Z0-9-]/', '', $test); 
echo $test . "
";

Additionally, I recommend using PHP_EOL instead of " " for newline characters.