Optimised PHP code for multiple input check - php

Question

There is a PHP update form where a user can update his records. The below-mentioned code looks redundant to me. How can I optimize this PHP code? Also, I have the admins username and email in a different table and the admin detail columns (such as first name, last name, gender, dob) in a different table. What will be the best way to check if username and email both have been updated or if any one of them and update it in the database accordingly.
Below is my source code:
if(isset($_POST['btnClick']) {
$f_name = NULL;
$l_name = NULL;
$username = NULL;
$email = NULL;
$gender = NULL;
$dob = NULL;
$f_name = filter_input(INPUT_POST, "f_name", FILTER_SANITIZE_STRING);
$l_name = filter_input(INPUT_POST, "l_name", FILTER_SANITIZE_STRING);
$username = filter_input(INPUT_POST, "username", FILTER_SANITIZE_STRING);
$email = filter_input(INPUT_POST, "email", FILTER_VALIDATE_EMAIL);
$gender = filter_input(INPUT_POST, "gender", FILTER_VALIDATE_STRING);
$dob = filter_input(INPUT_POST, "dob", FILTER_VALIDATE_STRING);
try {
if(isset($username) && $username != $_SESSION['username']) {
$sqlUpdate = "UPDATE admins SET username=:username WHERE admin_id=:admin_id";
/*Update code here...*/
echo "Username changed value inputted";
}
else if(isset($email) && $email != $_SESSION['email']) {
$sqlUpdate = "UPDATE admins SET username=:username WHERE admin_id=:admin_id";
/*Update code here...*/
echo "email change value inputted";
}
else if(isset($username) && isset($email)) {
/*Update both records */
}

Answer 1

You can do something like this:
<?php
try {
if (isset($username) && $username != $_SESSION['username']) {
$fieldsToUpdate[] = 'username=:username';
$updatedFields[] = 'Username';
}
if (isset($email) && $email != $_SESSION['email']) {
$fieldsToUpdate[] = 'email=:email';
$updatedFields[] = 'Email';
}
if (isset($fieldsToUpdate) && count($fieldsToUpdate) > 0) {
$sqlUpdate = "UPDATE admins SET " . implode($fieldsToUpdate, ', ') . " WHERE admin_id=:admin_id";
/*Update code here...*/
$finalMessage = 'Fields: ' . implode($updatedFields, ', ') . ' have been updated.';
}
}
PS: This is an example code that how can you optimize your code with PHP arrays and implode() function to run single query to update single or multiple fields.