php code for save and update using same button - php

Question

table name - user_table
i try to save and update value from single Save button.
but I can not understand how to merge save and update code in 'if else' using certain condition.
Below is my save code :
<?php
require_once('includes/config.php');
$errors = array();
$Admin = new admins;
if(isset($_POST['save']))
{
$errors = $Admin->validate_cms_user_table();
if(!count($errors))
{
$table = $Admin->user_table;
$fields_func = array ('password' =>"md5('{$_POST['password']}')");
unset ($_POST['password']);
if($Admin->save_advance($table,$_POST,$fields_func))
{
$_SESSION['message'] = "User Created Successfully";
header("Location:user_master.php");
exit;
}
}
}
?>
Update code
if($Admin->save($Admin->user_table,$_POST,"id=".$_GET['id']))
{
$_SESSION['message'] = "Updated Successfully";
header("Location: user_master.php");
exit;
}
Update Condition
if(!isset($_GET['catid']))
{
//Then Save Code
}
Else
{
//Update Code
}