In this article, we will learn how to validate a form using PHP. when the user submits the form, there are many chances that the user can enter wrong data, it may have security problems, so before inserting it into the database table, we must first validate the data and then insert it into the database.
Example
Let's make an HTML form and validate it
index.php
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>PHP Form Validation</title>
<link rel="stylesheet" href="https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css">
</head>
<style type="text/css">
.container {
max-width: 700px;
margin: 50px auto;
}
form {
border: 1px solid #000000;
background: #ecf5fc;
padding: 40px 50px 45px;
}
.form-control:focus {
border-color: #000;
box-shadow: none;
}
.error {
color: red;
font-weight: 400;
display: block;
padding: 6px 0;
font-size: 14px;
}
.form-control.error {
border-color: red;
padding: .375rem .75rem;
}
</style>
<body>
<div class="container mt-5">
<!-- Form validation script -->
<?php include('form_validation.php'); ?>
<!-- Contact form -->
<form action="" method="post">
<div class="form-group row">
<label class="col-sm-4 col-form-label">Name</label>
<div class="col-sm-8">
<input type="text" name="name" class="form-control">
<!-- Error -->
<?php echo $nameEmptyErr; ?>
<?php echo $nameErr; ?>
</div>
</div>
<div class="form-group row">
<label class="col-sm-4 col-form-label">Email</label>
<div class="col-sm-8">
<input type="email" name="email" class="form-control">
<!-- Error -->
<?php echo $emailEmptyErr; ?>
<?php echo $emailErr; ?>
</div>
</div>
<div class="form-group row">
<label class="col-sm-4 col-form-label">Education</label>
<div class="col-sm-8">
<select id="education" name="education" class="form-control">
<option selected="" disabled>...</option>
<option value="Graduation">Graduation</option>
<option value="Post Graduation">Post Graduation</option>
</select>
<!-- Error -->
<?php echo $educationEmptyErr; ?>
</div>
</div>
<fieldset class="form-group">
<div class="row">
<legend class="col-form-label col-sm-4 pt-0">Gender</legend>
<div class="col-sm-8">
<div class="custom-control custom-radio custom-control-inline">
<input type="radio" id="male" name="gender" value="Male" class="custom-control-input">
<label class="custom-control-label" for="male">Male</label>
</div>
<div class="custom-control custom-radio custom-control-inline">
<input type="radio" id="female" name="gender" value="Female" class="custom-control-input">
<label class="custom-control-label" for="female">Female</label>
</div>
<!-- Error -->
<?php echo $genderEmptyErr; ?>
</div>
</div>
</fieldset>
<div class="form-group row">
<div class="col-sm-4">Hobbies</div>
<div class="col-sm-8">
<div class="custom-control custom-checkbox custom-control-inline">
<input type="checkbox" name="hoby[]" value="Drawing" class="custom-control-input" id="drawing">
<label class="custom-control-label" for="drawing">Drawing</label>
</div>
<div class="custom-control custom-checkbox custom-control-inline">
<input type="checkbox" name="hoby[]" value="Singing" class="custom-control-input" id="singing">
<label class="custom-control-label" for="singing">Singing</label>
</div>
<div class="custom-control custom-checkbox custom-control-inline">
<input type="checkbox" name="hoby[]" value="Dancing" class="custom-control-input" id="dancing">
<label class="custom-control-label" for="dancing">Dancing</label>
</div>
<!-- Error -->
<?php echo $hobyEmptyErr; ?>
</div>
</div>
<div class="form-group row">
<label class="col-sm-4 col-form-label">Comment</label>
<div class="col-sm-8">
<textarea class="form-control" name="comment" id="comment" rows="4"></textarea>
<!-- Error -->
<?php echo $commentEmptyErr; ?>
</div>
</div>
<div class="form-group row">
<div class="col-sm-12 mt-3">
<button type="submit" name="submit" class="btn btn-primary btn-block">Submit</button>
</div>
</div>
</form>
</div>
</body>
</html>form_validation.php
<?php
// Error messages
$nameEmptyErr = "";
$emailEmptyErr = "";
$educationEmptyErr = "";
$genderEmptyErr = "";
$hobyEmptyErr = "";
$commentEmptyErr = "";
$nameErr = "";
$emailErr = "";
if (isset($_POST["submit"])) {
// Set form variables
$name = checkInput($_POST["name"]);
$email = checkInput($_POST["email"]);
if (!empty($_POST["education"])) {
$education = checkInput($_POST["education"]);
}
if (!empty($_POST["gender"])) {
$gender = checkInput($_POST["gender"]);
}
if (!empty($_POST["hoby"])) {
$hoby = $_POST["hoby"];
}
$comment = checkInput($_POST["comment"]);
// Name validation
if (empty($name)) {
$nameEmptyErr = '<div class="error">Name field can not be empty.</div>';
} // Allow letters and white space
else if (!preg_match("/^[a-zA-Z ]*$/", $name)) {
$nameErr = '<div class="error">Only letters and white space allowed.</div>';
} else {
echo $name . '<br>';
}
// Email validation
if (empty($email)) {
$emailEmptyErr = '<div class="error">Email field can not be empty.</div>';
} // E-mail format validation
else if (!preg_match("/^([a-z0-9\+_\-]+)(\.[a-z0-9\+_\-]+)*@([a-z0-9\-]+\.)+[a-z]{2,6}$/ix", $email)) {
$emailErr = '<div class="error">Email format is not valid.</div>';
} else {
echo $email . '<br>';
}
# code...
// Select option validation
if (empty($education)) {
$educationEmptyErr = '<div class="error">Tell us about your education.</div>';
} else {
echo $education . '<br>';
}
// Radio button validation
if (empty($gender)) {
$genderEmptyErr = '<div class="error">Specify your gender.</div>';
} else {
echo $gender . '<br>';
}
// Checkbox validation
if (!empty($hoby)) {
foreach ($_POST['hoby'] as $val) {
echo $val . '<br>';
}
} else {
$hobyEmptyErr = '<div class="error">What are your hobbies.</div>';
}
// Text-area validation
if (empty($comment)) {
$commentEmptyErr = '<div class="error">This field is required.</div>';
} else {
echo $comment . '<br>';
}
}
function checkInput($input) {
$input = trim($input);
$input = stripslashes($input);
$input = htmlspecialchars($input);
return $input;
}
?>Output:
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