Always JavaScript validation is he best practice. In almost all the web best applications we used JavaScript validation to make page fast and to give good user experience. The question is what if the JavaScript is disable. So in this post I given a simple example about “Server Side Form Validation using Regular Expressions “.

regular-expression-form-server-side-validation

Take a look at live demo.

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Demo

validation.php
Contains PHP code. eregi — Case insensitive regular expression match.

<?php
if($_POST)
{
$name = $_POST['name'];
$email = $_POST['email'];
$username = $_POST['username'];
$password = $_POST['password'];
$gender = $_POST['gender'];
// Full Name
if (eregi('^[A-Za-z0-9 ]{3,20}$',$name))
{
$valid_name=$name;
}
else
{
$error_name='Enter valid Name.';
}
// Email
if (eregi('^[a-zA-Z0-9._-]+@[a-zA-Z0-9._-]+.([a-zA-Z]{2,4})$', $email))
{
$valid_email=$email;
}
else
{
$error_email='Enter valid Email.';
}
// Usename min 2 char max 20 char
if (eregi('^[A-Za-z0-9_]{3,20}$',$username))
{
$valid_username=$username;
}
else
{
$error_username='Enter valid Username min 3 Chars.';
}
// Password min 6 char max 20 char
if (eregi('^[A-Za-z0-9!@#$%^&*()_]{6,20}$',$password))
{
$valid_password=$password;
}
else
{
$error_password='Enter valid Password min 6 Chars.';
}
// Gender
if ($gender==0)
{
$error_gender='Select Gender';
}
else
{
$valid_gender=$gender;
}

if((strlen($valid_name)>0)&&(strlen($valid_email)>0)
&&(strlen($valid_username)>0)&&(strlen($valid_password)>0) &&$valid_gender>0 )
{
mysql_query(" SQL insert statement ");
header("Location: thanks.html");
}
else{ }

}
?>

index.php
Contains HTML code. You have to include validation.php file.

<php include("validation.php"); ?>
<form method="post" action="" name="form">
Full name : <input type="text" name="name" value="<?php echo$valid_name; ?>" /> 
<?php echo $error_name; ?> 
Email : <input type="text" name="name" value="<?php echo$valid_email; ?>" /> 
<?php echo $error_email; ?> 
Username : <input type="text" name="name" value="<?php echo$valid_username; ?>" /> 
<?php echo $error_username; ?> 
Password : <input type="password" name="name" value="<?php echo$valid_password; ?>" /> 
<?php echo $error_password; ?> 
Gender : <select name="gender"> 
<option value="0">Gender</option>
<option value="1">Male</option>
<option value="2">Female</option>
</select>
<?php echo $error_gender; ?> 
</form>