thinkphp Member login password verification MD5 related issues

thinkphp Member Login Password verification MD5 issue.
Member Registration time password MD5 encrypted to the database, now member login to MD5 password after the database query should be how to write? I get the form MD5 after the database query why not the same, my Code is

Class Adminaction extends action{
       function index () {
  if (isset ($_post[' username ')) {
        if (isset ($_post[' username ')) &&isset ($_post[' password ']) {
    $secure _code = C (' Secure_code ');
    $userpassword =md5 ($secure _code.md5 ($_post["password"));
    $db =m ();
$select = $db->query ("SELECT * from developers where username=". $_post[' username ']. "and password=". $userpassword. "");
echo $db->getlastsql (); exit;

How should I write it?

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------Solution--------------------
On a login function you sent three posts in three consecutive days, you can not think about it, search for a solution
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MD5 ($secure _code.md5 ($_post["password"));

This is the original password to add something, in the verification of the time you also add not to be finished
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1: $userpassword =md5 ($secure _code.md5 ($_post["password")); Why MD5 to encrypt two times?
2: Since the last statement printed, the password of the MD5 with the eyes and the database encrypted comparison, is it consistent?
------Solution--------------------
References:

MD5 ($secure _code.md5 ($_post["password"));

This is the original password to add something, in the verification of the time you also add not to be finished

+1! It turns out how you encrypt before you put it in the database. Copy the statement.
------Solution--------------------
Are you sure the encryption method is the same when inserting and querying?

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