Need Simple help in PHP

<?php session_start(); 
	
	if(isset($_POST['Submit'])){
		$logins = array('username' => 'password','' => '');
		
		$Username = isset($_POST['Username']) ? $_POST['Username'] : '';
		$Password = isset($_POST['Password']) ? $_POST['Password'] : '';
		
		if (isset($logins[$Username]) && $logins[$Username] == $Password){
			$_SESSION['UserData']['Username']=$logins[$Username];
			header("location:location.php");
			exit;
		} else {
			$msg="<span style='color:red'>Invalid Login Details</span>";
		}
	}
?>
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>Login to continue</title>
<link href="./css/style.css" rel="stylesheet">
</head>
<body>
<div id="Frame0">
  <h1>Login</h1>
</div>
<br>
<form action="" method="post" name="Login_Form">
  <table width="400" border="0" align="center" cellpadding="5" cellspacing="1" class="Table">
    <?php if(isset($msg)){?>
    <tr>
      <td colspan="2" align="center" valign="top"><?php echo $msg;?></td>
    </tr>
    <?php } ?>
    <tr>
      <td colspan="2" align="left" valign="top"><h3>Login</h3><h3><a href=""></h3></td>
    </tr>
    <tr>
      <td align="right" valign="top">Username</td>
      <td><input name="Username" type="text" class="Input"></td>
    </tr>
    <tr>
      <td align="right">Password</td>
      <td><input name="Password" type="password" class="Input"></td>
    </tr>
    <tr>
      <td>&nbsp;</td>
      <td><input name="Submit" type="submit" value="Login" class="Button3"></td>
    </tr>
  </table>
  
</form>
</body>
</html>

i have this simple php login code in which it requires username and password to login that are in array i don’t know much about php i need to use only password and not username can someone please correct it?

Not sure what you are trying to achieve here or how you want to use password without a username, but the data in $_POST is an array of data submitted from your form.
https://www.w3schools.com/php/php_superglobals_post.asp