下面这段代码解决了我的问题:

This code below solved my problem:

if (!preg_match("/^(([^0]{1})([0-9])*|(0{1}))(\,\d{2}){0,1}€?$/", $form['salary'])) {
    echo "invalid";
    return false;
} else {
    $value1 = 400;
    $value2 = 10000;
    $salary = $form['salary'];
    $salary = preg_replace('/[€]/i', '', $salary);
    if($salary < $value1 || $salary > $value2) {
        echo "bad values";
        return false;
    } else {
        echo "valid";
        return true;
    }
}