How to validate form field in php

Question

I have a registration form that has some required field. i want to check if those required fields are filled and if they are filled correctly before i insert in my database.

One of the required field is email, i also want to check if the email entered is a valid email.

My code is below.

Thanks in advance for your help, i really appreciate it.

<?php
include 'config.php';
$tbl_name="citizens"; // Table name
// Get values from form and formatting them as SQL strings
$firstname = mysql_real_escape_string($_POST['firstname']);
$middlename = mysql_real_escape_string($_POST['middlename']);
$lastname = mysql_real_escape_string($_POST['lastname']);
$sex = mysql_real_escape_string($_POST['sex']);
$address = mysql_real_escape_string($_POST['address']);
$employer = mysql_real_escape_string($_POST['employer']);
$posincom = mysql_real_escape_string($_POST['posincom']);
$states = mysql_real_escape_string($_POST['states']);
$agerange = mysql_real_escape_string($_POST['agerange']);
$income = mysql_real_escape_string($_POST['income']);
$email = mysql_real_escape_string($_POST['email']);
$phone = mysql_real_escape_string($_POST['phone']);

// Insert data into mysql 
$sql="INSERT INTO `$tbl_name` (firstname, middlename, lastname, sex, address, employer, position_in_company, states, age_range, local_govt_area, email, phone) VALUES('$firstname', '$middlename', '$lastname', '$sex', '$address', '$employer', '$posincom', '$states', '$agerange', '$income', '$email', '$phone')";
$result=mysql_query($sql);

// if successfully insert data into database, displays message "Successful". 
if($result){
echo "You Have Successful Registered";
}else {
echo "Sorry!!! Could Not Register You. All a* fields must be field.";
}
?>

Answer 1

<?php
include 'config.php';
$tbl_name="citizens"; // Table name

$required = array('email');
$errors = array();

foreach($required as $required_fieldname){
    if(!isset($_POST[$required_fieldname]) || empty($_POST[$required_fieldname])){
        $errors[] = 'Sorry!!! Could Not Register You. All a* fields must be field.';
        break;
    }
}

if(isset($_POST['email']) && !filter_var($_POST['email'], FILTER_VALIDATE_EMAIL)){
    $errors[] = "That is not a valid email address.";
}

if(count($errors) == 0){
    // Get values from form and formatting them as SQL strings
    $firstname = mysql_real_escape_string($_POST['firstname']);
    $middlename = mysql_real_escape_string($_POST['middlename']);
    $lastname = mysql_real_escape_string($_POST['lastname']);
    $sex = mysql_real_escape_string($_POST['sex']);
    $address = mysql_real_escape_string($_POST['address']);
    $employer = mysql_real_escape_string($_POST['employer']);
    $posincom = mysql_real_escape_string($_POST['posincom']);
    $states = mysql_real_escape_string($_POST['states']);
    $agerange = mysql_real_escape_string($_POST['agerange']);
    $income = mysql_real_escape_string($_POST['income']);
    $email = mysql_real_escape_string($_POST['email']);
    $phone = mysql_real_escape_string($_POST['phone']);

    // Insert data into mysql 
    $sql="INSERT INTO `$tbl_name` (firstname, middlename, lastname, sex, address, employer, position_in_company, states, age_range, local_govt_area, email, phone) VALUES('$firstname', '$middlename', '$lastname', '$sex', '$address', '$employer', '$posincom', '$states', '$agerange', '$income', '$email', '$phone')";
    $result= mysql_query($sql);

    // if successfully insert data into database, displays message "Successful". 
    if($result){
        echo "You Have Successfully Registered";
    }else {
        echo "A technical error has occured.";
    }
}
else{
    echo '<strong>ERRORS!</strong><br>';
    foreach($errors as $error){
        echo $error . '<br>';
    }
}
?>

Answer 2

you should validate form before submitting at client side using JavaScript, and alert to user if not filled correctly. Once validated allow it to submit . In other case it is overhead to validate at server and than again send response to user at client end.

Answer 3

For email you can use this (or similar) functions from https://stackoverflow.com/questions/3314493/check-for-valid-email-address to validate email

function isValidEmail($email){
    return preg_match("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$^", $email);
}

Or

function isValidEmail( $email ){
    return filter_var( $email, FILTER_VALIDATE_EMAIL );
}

For the rest, you can use the following

<?php
    $error = '';

    //put chosen function here
    function isValidEmail( $email ){
        return filter_var( $email, FILTER_VALIDATE_EMAIL );
    }

    //get values and validate each one as required
    $firstname = mysql_real_escape_string($_POST['firstname']);
        if(!$firstname){ $error .= "First name is required<br />"; }

    //repeat for each field
    $email = mysql_real_escape_string($_POST['email']);
        if(!isValidEmail($email)){ $error .= "The email entered is invalid<br />"; }

    //and so on...

    if(!$error){
         //add insert into database code here
    }
    else{
        //display $error however you want e.g....
        echo "<div class=\"error\">$error</div>";
    }
?>

Answer 4

<?php
include 'config.php';
$tbl_name="citizens"; // Table name
// Get values from form and formatting them as SQL strings

//your other fields ...
$email = mysql_real_escape_string($_POST['email']);
if(!filter_var($email, FILTER_VALIDATE_EMAIL)){ 
$errors = 1;
echo "Please enter a correct email address";
}

//similar approach can be used for other fields..
// this is one of the simplest validating approach


if($errors == 0){
// Insert data into mysql 
$sql="INSERT INTO `$tbl_name` (firstname, middlename, lastname, sex, address, employer, position_in_company, states, age_range, local_govt_area, email, phone) VALUES('$firstname', '$middlename', '$lastname', '$sex', '$address', '$employer', '$posincom', '$states', '$agerange', '$income', '$email', '$phone')";
$result=mysql_query($sql);

// if successfully insert data into database, displays message "Successful". 
if($result){
echo "You Have Successful Registered";
}else {
echo "Sorry!!! Could Not Register You. All a* fields must be field.";
}
}
?>

Answer 5

1.) you can use PHP_FILTER for validation.

2.) you can proper check( variable is null or not) before insert the data if variable is null the display error msg otherwish insert..