PHP password login

Would this PHP script be considered a reasonably secure login method to view a web page?

======================

<?php 
// Define your username and password 
$username = "someuser"; 
$password = "somepassword";
if ($_POST['txtUsername'] != $username || $_POST['txtPassword'] != $password) {
?> 
<h1>Login</h1> 
<form name="form" method="post" action="<?php echo$_SERVER['PHP_SELF']; ?>">
<p><label for="txtUsername">Username:</label>
<br /><input type="text" title="Enter your Username" name="txtUsername" /></p>
<p><label for="txtpassword">Password:</label>
<br /><input type="password" title="Enter your password" name="txtPassword" /></p>
<p><input type="submit" name="Submit" value="Login" /></p>
</form> 
<?php 
} 
else {
?> 
<p>This is the protected page. Your private content goes here.</p> 
<?php 
} 
?> 

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