Password_hash Incorrect after updating table - php

Question

My login system md5 hashes the username and I password_hash the password. Therefore I cannot fetch the row based on the username? My client then enters an email address which I base64encode. I then offer a lost password change option. However, when I UPDATE the field using the same type of hash but, using the email field as an identifier, the new password is incorrect?
Below is a sample of my UPDATE, but hard coded for illustration(PS this does not work either?).
$em = 'example#example.com';
$em1 = base64_encode($em);
$ps = 'some password';
$password_hash = password_hash($ps, PASSWORD_BCRYPT);
$qu = "UPADTE table SET field = '$password_hash' WHERE email = '$em1'";
$res = mysqli_query($link, $qu);
Edited question to include my code after verifying that the user exists and sending out an email for them to positively identify themselves as the owner of the account. Here is the final processor page.
if(EMPTY($_POST[psw1]) ) {
echo "New password must be supplied"; }
elseif(EMPTY($_POST[psw2]) ) {
echo "Repeat password must be entered"; }
elseif($_POST[psw1] != $_POST[psw2]) {
echo "Passwords entered do not match";
} elseif(EMPTY($_POST[eu])) {
echo "Essential data is missing in order to complete this process.";
}
elseif (strlen($_POST['psw1']) < 6) {
echo "Password must be at least six characters in length";
}
elseif (preg_replace("/[^a-zA-Z0-9]/", "", $_POST['psw1']) != $_POST['psw1']) {
echo "Password may only contain letters and numbers";
}
elseif(!EMPTY($_POST[psw1]) && !EMPTY($_POST[psw2]) && !EMPTY($_POST[eu]) && $_POST[pw1] == $_POST[pw2] ) {
include "conn.php";
echo "$_POST[eu]<br />";
$eu = $_POST[eu];
$pdw = password_hash($_POST[pw1], PASSWORD_BCRYPT);
$sq = mysqli_query($link, "UPDATE str1 SET pf = '$pdw', cu_pw_status = '2' WHERE cu_type = '$eu'");
echo "Your password has been changed, you may now login <a href='login2.php'>Login</a>";
} else {
echo "An error occured. Contact Site Admin"; }

Answer 1

Check if you have column 'field' in your users table. Seems suspicios.
Check your update string, now it misses table name.
Check if you have user before updating:
$exists = mysqli_query("SELECT id FROM users WHERE email='$em1');
if (!is_empty($exists)) {
mysqli_query("UPDATE TABLE users SET password = '$ps' WHERE id='$exists');
echo 'updated' . "\n";
} else {
echo 'no user with such email hash' . "\n";
}