I am creating a project on the school management system using PHP and I am stuck as it's giving me an error: Cannot modify header information - headers already sent. If the user forgot to fill any field and click on the submit button,the server should return a message like fill this field but instead it's giving this error and I don't know why.
this is the error I am getting
this is my form
This is my home page
<?php
session_start();
require_once 'header.php';
if(!isset($_SESSION['name']))
{
die("Access Denied");
}
if(isset($_POST['logout']))
{
header('Location: logout.php');
return;
}
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<link rel="stylesheet" href="https://pro.fontawesome.com/releases/v5.10.0/css/all.css"
integrity="sha384-AYmEC3Yw5cVb3ZcuHtOA93w35dYTsvhLPVnYs9eStHfGJvOvKxVfELGroGkvsg+p" crossorigin="anonymous"/>
<link href="https://fonts.googleapis.com/css2?family=Poppins:wght@400;500&display=swap" rel="stylesheet">
<link href="https://fonts.googleapis.com/css2?family=Roboto:wght@300;400;500&display=swap" rel="stylesheet">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/chart.js@2.8.0"></script>
<link rel="stylesheet" href="style.css">
<link rel="stylesheet" href="../management/dashboard/css/admin.css">
<link rel="stylesheet" href="../management/student/css/addstudent.css">
<link rel="stylesheet" href="../management/student/css/allstudent.css">
<link rel="stylesheet" href="../management/student/css/studentdetail.css">
</head>
<body>
<header>
<nav>
<div class="logo">
<div class="img">
<img src="./images/logo3.png" alt="">
</div>
</div>
<ul class="nav-links">
<li id="n-1">
<div class="admin">
<p>Konark Shivam</p>
<i class="fas fa-user-circle"></i>
</div>
</li>
<li id="n-2">
<i class="fas fa-envelope"></i>
</li>
<li id="n-3">
<i class="fas fa-bell"></i>
</li>
<li id="n-4">
<i class="fas fa-sign-out-alt"></i>
</li>
</ul>
<div class="burger" id="burger">
<i class="fas fa-bars"></i>
</div>
</nav>
</header>
<!-- for logout -->
<section>
<div class="logout-box" id="logout-box">
<div class="logout-content">
<p>Do you want to logout</p>
<form method="post">
<div class="logout-button">
<input type="submit" name="logout" value="Logout">
<input type="submit" name="cancel" value="Cancel" id="logout-cancel" onclick="return false">
</div>
</form>
</div>
</div>
</section>
<menu>
<div class="left-menu" id="left-menu">
<ul>
<li class="menu-items" id="menu-item-1">
<a href="#">Dashboard</a>
<span class="arrow">></span>
</li >
<div class="drop-menu" id="drop-menu-1">
<ul>
<li class="drop-items">
<div class="name"></div>
<a id="d-i-admin" href="home.php?page=dashboard/admin">> Admin</a>
</li>
<li class="drop-items">
<div class="name"></div>
<a href="#" id="d-i-teacher">> Teacher</a>
</li>
<li class="drop-items">
<div class="name"></div>
<a href="#">> Students</a>
</li>
<li class="drop-items">
<div class="name"></div>
<a href="#">> Parents</a>
</li>
</ul>
</div>
<li class="menu-items" id="menu-item-2">
<span>Student</span>
<span class="arrow">></span>
</li>
<div class="drop-menu" id="drop-menu-2">
<ul>
<li class="drop-items">
<div class="name"></div>
<a href="home.php?page=student/allstudent" id="s-d-1">> All Students </a>
</li>
<li class="drop-items">
<div class="name"></div>
<a href="home.php?page=student/studentdetail">> Student Details</a>
</li>
<li class="drop-items">
<div class="name"></div>
<a href="home.php?page=student/addstudent">> Admission Form</a>
</li>
<li class="drop-items">
<div class="name"></div>
<a href="#">> Student Promotion</a>
</li>
</ul>
</div>
<li class="menu-items" id="menu-item3">
<span>Teacher</span>
<span class="arrow">></span>
</li>
<div class="drop-menu" id="drop-menu-3">
<ul>
<li class="drop-items">
<div class="name"></div>
<a href="#">> Admin</a>
</li>
<li class="drop-items">
<div class="name"></div>
<a href="#">> Teacher</a>
</li>
<li class="drop-items">
<div class="name"></div>
<a href="#">> Students</a>
</li>
<li class="drop-items">
<div class="name"></div>
<a href="#">> Parents</a>
</li>
</ul>
</div>
<li class="menu-items">
<span>Parents</span>
<span class="arrow">></span>
</li>
<li class="menu-items">
<span>Library</span>
<span class="arrow">></span>
</li>
<li class="menu-items">
<span>Subjects</span>
<span class="arrow">></span>
</li>
<li class="menu-items">
<span>Class Routines</span>
<span class="arrow">></span>
</li>
<li class="menu-items">
<span>Attendence</span>
<span class="arrow">></span>
</li>
<li class="menu-items">
<span>Exams</span>
<span class="arrow">></span>
</li>
<li class="menu-items">
<span>Transport</span>
<span class="arrow">></span>
</li>
<li class="menu-items">
<span>Hostel</span>
<span class="arrow">></span>
</li>
<li class="menu-items">
<span>Notice</span>
<span class="arrow">></span>
</li>
<li class="menu-items">
<span>Message</span>
<span class="arrow">></span>
</li>
<li class="menu-items">
<span>Accounts</span>
<span class="arrow">></span>
</li>
</ul>
</div>
</menu>
<main>
<div class="presentation">
<div class="my-container" id="container">
<?php
if(isset($_GET['page']))
{
$page=$_GET['page'];
include_once $page.'.php';
}
else{
include_once 'dashboard/admin.php';
}
?>
</div>
</div>
</main>
<script src="script.js"></script>
</body>
</html>
this is my addstudent page
<?php
ob_start();
if(!isset($_SESSION['name']))
{
die("Access Denied");
}
require_once 'pdo.php';
if(isset($_POST['submit']))
{
if(isset($_POST['f_name']) && isset($_POST['l_name']) && isset($_POST['gender']) && isset($_POST['dob']) && isset($_POST['blood'])
&& isset($_POST['religion']) && isset($_POST['email']) && isset($_POST['address']) && isset($_POST['phone']) )
{
if(strlen($_POST['f_name'])<1)
{
$_SESSION['error']='Please enter first name';
header('Location:home.php?page=student/addstudent');
return;
}
if(strlen($_POST['l_name'])<1)
{
$_SESSION['error']='Please enter last name';
header('Location:addstudent.php');
return;
}
if(strlen($_POST['gender'])<1)
{
$_SESSION['error']='Please enter gender';
header('Location:addstudent.php');
return;
}
if(strlen($_POST['dob'])<1)
{
$_SESSION['error']='Please select date';
header('Location:addstudent.php');
return;
}
if(strlen($_POST['blood'])<1)
{
$_SESSION['error']='Please enter blood group';
header('Location:addstudent.php');
return;
}
if(strlen($_POST['religion'])<1)
{
$_SESSION['error']='Please enter religion';
header('Location:addstudent.php');
return;
}
if(strlen($_POST['email'])<1)
{
$_SESSION['error']='Please enter email';
header('Location:addstudent.php');
return;
}
else if(!strpos($_POST['email'],"@")>0)
{
$_SESSION['error']='Please enter valid email';
header('Location:addstudent.php');
return;
}
if(strlen($_POST['address'])<1)
{
$_SESSION['error']='Please Address';
header('Location:addstudent.php');
return;
}
if(is_numeric($_POST['phone'])!=1)
{
$_SESSION['error']='Please enter valid phone no';
header('Location:addstudent.php');
return;
}
else
{
$stmpt=$pdo->prepare('INSERT INTO student_detail (f_name ,l_name ,gender, dob, blood_grp, religion, email, phone, address)
VALUES ( :fn , :ln , :sx , :dob , :bld , :re , :em , :phno , :add )');
$stmpt->execute(array(
':fn'=>$_POST['f_name'],
':ln'=>$_POST['l_name'],
':sx'=>$_POST['gender'],
':dob'=>$_POST['dob'],
':bld'=>$_POST['blood'],
':re'=>$_POST['religion'],
':em'=>$_POST['email'],
':phno'=>$_POST['phone'],
':add'=>$_POST['address']
));
$_SESSION['success']='Profile added';
header("Location: addstudent.php");
return;
}
}
}
ob_end_flush();
?>
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
<link rel="stylesheet" href="../student/css/addstudent.css">
</head>
<body>
<div class="container-student-3">
<div class="page-info">
<h3>Student Form</h3>
<p>Home>Student Admit form</p>
</div>
<div class="server-message">
<?php
if(isset($_SESSION['error']))
{
echo '<p style="color:red";>'.$_SESSION['error'].'</p>';
unset($_SESSION['error']);
}
if(isset($_SESSION['success']))
{
echo '<p style="color:green";>'.$_SESSION['success'].'</p>';
unset($_SESSION['success']);
}
?>
</div>
<div class="student-form-wrap">
<div class="student-form-content">
<h3>Add New Student</h3>
<form method="post">
<div class="form-inputs">
<div class="col-xl-3 col-lg-6 col-12 form-group">
<label>First Name *</label>
<input type="text" placeholder="First Name" name="f_name" class="form-control">
</div>
<div class="col-xl-3 col-lg-6 col-12 form-group">
<label>Last Name *</label>
<input type="text" placeholder="Last Name" name="l_name" class="form-control">
</div>
<div class="col-xl-3 col-lg-6 col-12 form-group">
<label>Gender *</label>
<input type="text" placeholder="Gender" name="gender" class="form-control">
</div>
<div class="col-xl-3 col-lg-6 col-12 form-group">
<label>Date Of Birth *</label>
<input type="date" placeholder="Date of Birth" name="dob" class="form-control">
</div>
<div class="col-xl-3 col-lg-6 col-12 form-group">
<label>Blood Group *</label>
<input type="text" placeholder="Blood Group" name="blood" class="form-control">
</div>
<div class="col-xl-3 col-lg-6 col-12 form-group">
<label>Religion *</label>
<input type="text" placeholder="Religion" name="religion" class="form-control">
</div>
<div class="col-xl-3 col-lg-6 col-12 form-group">
<label>E-Mail *</label>
<input type="text" placeholder="E-male" name="email" class="form-control">
</div>
<div class="col-xl-3 col-lg-6 col-12 form-group">
<label>Address *</label>
<input type="text" placeholder="Address" name="address" class="form-control">
</div>
<div class="col-xl-3 col-lg-6 col-12 form-group">
<label>Phone *</label>
<input type="text" placeholder="Phone No" name="phone" class="form-control">
</div>
<div class="col-12 form-group mg-t-8">
<input type="submit" value="submit" name="submit">
<input type="reset" value="Reset" id="reset">
</div>
</div>
</form>
</div>
</div>
</div>
</body>
</html>
