PHP password validation

I made a registration validation in PHP and I'm troubleshooting each field to see if the code works to par. When I press the submit button the only part not working is the password / confirm password code block. I've been troubleshooting for hours and can't seem to find the issue.

Is possible someone can point out the issue? Thanks.

<?php
// define variables and set to empty values
$emailErr = $userErr = $passwordErr = $cpasswordErr = $firstErr = $lastErr = $teamErr = "";
$email = $username = $password = $cpassword = $firstname = $lastname = $teamname = "";

// The preg_match() function searches a string for pattern, returning true if the pattern exists, and false otherwise.
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    //Validates email
    if (empty($_POST["email"])) {
        $emailErr = "You Forgot to Enter Your Email!";
    } else {
        $email = test_input($_POST["email"]);
        // check if e-mail address syntax is valid
        if (!preg_match("/([\w\-]+\@[\w\-]+\.[\w\-]+)/",$email)) {
            $emailErr = "You Entered An Invalid Email Format"; 
        }
    }
    //Validates Username
    if (empty($_POST["username"])) {
        $userErr = "You Forgot to Enter Your Username!";
    } else {
        $username = test_input($_POST["username"]);
        }
    //Validates password & confirm passwords.
    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 {
            $cpasswordErr = "Please Check You've Entered Or Confirmed Your Password!";
        }
    }
    //Validates firstname
    if (empty($_POST["firstname"])) {
        $firstErr = "You Forgot to Enter Your First Name!";
    } else {
        $firstname = test_input($_POST["firstname"]);
        //Checks if name only contains letters and whitespace
        if (!preg_match("/^[a-zA-Z ]*$/",$firstname)) {
            $firstErr = "Only letters and white space allowed"; 
        }
    }
   if (empty($_POST["lastname"])) {
        $lastErr = "You Forgot to Enter Your Last Name!";
    } else {
        $lastname = test_input($_POST["lastname"]);
        //Checks if name only contains letters and whitespace
        if (!preg_match("/^[a-zA-Z ]*$/",$lastname)) {
            $lastErr = "Only letters and white space allowed"; 
        }
    }
    if (empty($_POST["teamname"])) {
        $teamErr = "You Forgot to Enter Your Team Name!";
    } else {
        $teamname = test_input($_POST["teamname"]);
    }
}
/*Each $_POST variable with be checked by the function*/
function test_input($data) {
     $data = trim($data);
     $data = stripslashes($data);
     $data = htmlspecialchars($data);
     return $data;
}
?>