Computer Programming (php code for linking login/sign up page)

I thought sharing this will help people who has passion for programming, i will be sharing some php codes that you can use to link up your sign up and login page when developing a full, well functional website.

1. The php code for a standard signup page;

• step 1: copy the code below into a notepad++, so that you can edit before you can make use of it.

<?php
require('includes/config.php');

if(!empty($_POST))
{
    $msg="";
    
    if(empty($_POST['firstname']) || empty($_POST['username']) || empty($_POST['gender']) || empty($_POST['password']) || empty($_POST['confirmpassword']) || empty($_POST['email'])||empty($_POST['city']))
    {
        $msg.="<li>Please full fill all requirement";
    }
    
    if($_POST['password']!=$_POST['confirmpassword'])
    {
        $msg.="<li>Please Enter your Password Again.....";
    }
    
    if(!ereg("^[a-z0-9_]+[a-z0-9_.]*@[a-z0-9_-]+[a-z0-9_.-]*\.[a-z]{2,5}$",$_POST['mail']))
    {
        $msg.="<li>Please Enter Your Valid Email Address...";
    }
    
    
    if(strlen($_POST['password'])>10)
    {
        $msg.="<li>Please Enter Your Password in limited Format....";
    }
    
    if(is_numeric($_POST['firstname']))
    {
        $msg.="<li>Name must be in String Format...";
    }
    
    if($msg!="")
    {
        header("location:register.php?error=".$msg);
    }
    else
    {
        $firstname=$_POST['firstname'];
        $username=$_POST['username'];
        $password=$_POST['password'];
        $gender=$_POST['gender'];
        $email=$_POST['mail'];
        $contact=$_POST['contact'];
        $city=$_POST['city'];
        
        $query="insert into user(u_firstname,u_username,u_password,u_gender,u_email,u_contact,u_city)
        values('$firstname','$username','$password','$gender','$email','$contact','$city')";
        
        mysqli_query($conn,$query) or die("Can't Execute Query...");
        header("location:register.php?ok=1");
    }
}
else
{
    header("location:index.php");
}
?> 

2. For the login page, follow the same instruction above and you will thank me later

     <?php session_start();

  require('includes/config.php');

if(!empty($_POST))
{
    $msg="";
    
    if(empty($_POST['username']))
    {
        $msg[]="No such User";
    }
    
    if(empty($_POST['password']))
    {
        $msg[]="Password Incorrect........";
    }
    
    
    if(!empty($msg))
    {
        echo '<b>Error:-</b><br>';
        
        foreach($msg as $k)
        {
            echo '<li>'.$k;
        }
    }
    else
    {
        
        

        
        $username=$_POST['username'];
        
        $q="select * from user where u_username='$username'";
        
        $res=mysqli_query($conn,$q) or die("wrong query");
        
        $row=mysqli_fetch_assoc($res);
        
        if(!empty($row))
        {
            if($_POST['password']==$row['u_password'])
            {
                $_SESSION=array();
                $_SESSION['username']=$row['u_username'];
                $_SESSION['uid']=$row['u_pwd'];
                $_SESSION['status']=true;
                
                if($_SESSION['username']!="admin")
                {
                    header("location:index.php");
                }
                else
                {
                    header("location:admin/index.php");
                }
            }
            
            else
            {
                echo 'Incorrect Password....';
            }
        }
        else
        {
            echo 'Invalid User';
        }
    }

}
else
{
    header("location:index.php");
}

?>