if(!empty($_POST["password"]) && ($_POST["password"] == $_POST["cpassword"])) {
    $password = test_input($_POST["password"]);
    $cpassword = test_input($_POST["cpassword"]);
    if (strlen($_POST["password"]) <= 8) {
        $passwordErr = "Your Password Must Contain At Least 8 Characters!";
    }
    elseif(!preg_match("#[0-9]+#",$password)) {
        $passwordErr = "Your Password Must Contain At Least 1 Number!";
    }
    elseif(!preg_match("#[A-Z]+#",$password)) {
        $passwordErr = "Your Password Must Contain At Least 1 Capital Letter!";
    }
    elseif(!preg_match("#[a-z]+#",$password)) {
        $passwordErr = "Your Password Must Contain At Least 1 Lowercase Letter!";
    } else {
        $cpasswordErr = "Please Check You've Entered Or Confirmed Your Password!";
    }
}

应该是:

if(!empty($_POST["password"]) && ($_POST["password"] == $_POST["cpassword"])) {
    $password = test_input($_POST["password"]);
    $cpassword = test_input($_POST["cpassword"]);
    if (strlen($_POST["password"]) <= '8') {
        $passwordErr = "Your Password Must Contain At Least 8 Characters!";
    }
    elseif(!preg_match("#[0-9]+#",$password)) {
        $passwordErr = "Your Password Must Contain At Least 1 Number!";
    }
    elseif(!preg_match("#[A-Z]+#",$password)) {
        $passwordErr = "Your Password Must Contain At Least 1 Capital Letter!";
    }
    elseif(!preg_match("#[a-z]+#",$password)) {
        $passwordErr = "Your Password Must Contain At Least 1 Lowercase Letter!";
    }
}
elseif(!empty($_POST["password"])) {
    $cpasswordErr = "Please Check You've Entered Or Confirmed Your Password!";
} else {
     $passwordErr = "Please enter password   ";
}

您对不匹配密码的检查是在 if 中检查它们是否匹配.

Your check for the non-matching passwords was within an if that checked to see if they matched.