Description:
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I use crypt, I use the first 2 letters of the username and create a encryption, like below under encryption then database $password into the database
perfect.
Now I come to where I am testing to see if it matches someone goes to login in, they enter username, and password, I take there username, user it as salt to encrypt there password in the same way, I take there username, and there password and run it against the db for a match, if it matches it returns true and pulls the result.
If it doesn't it returns false
supposedly, if it's just 1 character off then it doesn't work.
I used 951103902 for instance
if I add an extra letter at the end, or change one before it, it still returns true, I tried it with random words too, this isn't suppose to happen.

Reproduce code:
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//encrypt
$salt = substr($username, 0, 2);
$password = crypt($password, $salt);
//decrypt
$salt = substr($username, 0, 2);
$enteredpass = crypt($enteredpass, $salt);
if ($enteredpass === $password){
echo "The passwords match";
}else {
echo "The password is incorrect";
}

Expected result:
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I expect it to encrypt the password using crypt with the first 2 letters of whatever username.
which it does
then when I go to retrieve it with the persons entered information, if they typed the same password and username earlier, I expect it to get a match on the password, but it doesn't

Actual result:
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it doesn't match all the time, it does if it's right, if it's way off it returns false, which is good, but if it's close to a match but a little off it returns true