form validation in php example
Posted By
Bajarangi soft ,
Posted On 02-02-2024
Form Validation is a necessary process before the data entered in the form is submitted to the database.
Form Validation In PHP
Form Validation is a necessary process before the data entered in the form is submitted to the database. This is done to avoid unnecessary errors. In PHP Form validation, the script checks for data in respective fields based on the rules set by the developer, and returns an error if it does not meet the requirements.
An HTML form contains various input fields such as text box, checkbox, radio buttons, submit button, and checklist, etc. These input fields need to be validated, which ensures that the user has entered information in all the required fields and also validates that the information provided by the user is valid and correct.
In Validation you need to validate a few things as below,
Empty String
The code below checks that the field is not empty. If the user leaves the required field empty, it will show an error message.
if ( empty($_POST["name"])) {
$errMsg = "Error! You didn't enter the Name.";
echo $errMsg;
} else {
$name = $_POST["name"];
}
Validate String
The code below checks that the field will contain only alphabets and whitespace.
$name = $_POST ["Name"];
if (!preg_match ("/^[a-zA-z]*$/", $name) ) {
$ErrMsg = "Only alphabets and whitespace are allowed.";
echo $ErrMsg;
} else {
echo $name;
}
Validate Number
The below code validates that the field will only contain a numeric value.
$mobileno = $_POST ["Mobile_no"];
if (!preg_match ("/^[0-9]*$/", $mobileno) ){
$ErrMsg = "Only numeric value is allowed.";
echo $ErrMsg;
} else {
echo $mobileno;
}
Validate Email
A valid email must contain @ and . symbols. PHP provides various methods to validate the email address. Here, we will use regular expressions to validate the email address.
The below code validates the email address provided by the user through HTML form. If the field does not contain a valid email address, then the code will display an error message,
$email = $_POST ["Email"];
$pattern = "^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$^";
if (!preg_match ($pattern, $email) ){
$ErrMsg = "Email is not valid.";
echo $ErrMsg;
} else {
echo "Your valid email address is: " .$email;
}
Input Length Validation
The input length validation restricts the user to provide the value between the specified range.
$mobileno = strlen ($_POST ["Mobile"]);
$length = strlen ($mobileno);
if ( $length < 10 && $length > 10) {
$ErrMsg = "Mobile must have 10 digits.";
echo $ErrMsg;
} else {
echo "Your Mobile number is: " .$mobileno;
}
Validate URL
The code below validates the website URL provided by the user via HTML form. If the field does not contain a valid URL.
$websiteURL = $_POST["website"];
if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$website)) {
$websiteErr = "URL is not valid";
echo $websiteErr;
} else {
echo "Website URL is: " .$websiteURL;
}
Example : now let's create a form and apply validation on it,
<!DOCTYPE html>
<html>
<head>
<style>
.error {color: #FF0001;}
</style>
</head>
<body>
<?php
// define variables to empty values
$nameErr = $emailErr = $mobilenoErr = $genderErr = $websiteErr = $agreeErr = "";
$name = $email = $mobileno = $gender = $website = $agree = "";
//Input fields validation
if ($_SERVER["REQUEST_METHOD"] == "POST") {
//String Validation
if (emptyempty($_POST["name"])) {
$nameErr = "Name is required";
} else {
$name = input_data($_POST["name"]);
// check if name only contains letters and whitespace
if (!preg_match("/^[a-zA-Z ]*$/",$name)) {
$nameErr = "Only alphabets and white space are allowed";
}
}
//Email Validation
if (emptyempty($_POST["email"])) {
$emailErr = "Email is required";
} else {
$email = input_data($_POST["email"]);
// check that the e-mail address is well-formed
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
$emailErr = "Invalid email format";
}
}
//Number Validation
if (emptyempty($_POST["mobileno"])) {
$mobilenoErr = "Mobile no is required";
} else {
$mobileno = input_data($_POST["mobileno"]);
// check if mobile no is well-formed
if (!preg_match ("/^[0-9]*$/", $mobileno) ) {
$mobilenoErr = "Only numeric value is allowed.";
}
//check mobile no length should not be less and greator than 10
if (strlen ($mobileno) != 10) {
$mobilenoErr = "Mobile no must contain 10 digits.";
}
}
//URL Validation
if (emptyempty($_POST["website"])) {
$website = "";
} else {
$website = input_data($_POST["website"]);
// check if URL address syntax is valid
if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$website)) {
$websiteErr = "Invalid URL";
}
}
//Empty Field Validation
if (emptyempty ($_POST["gender"])) {
$genderErr = "Gender is required";
} else {
$gender = input_data($_POST["gender"]);
}
//Checkbox Validation
if (!isset($_POST['agree'])){
$agreeErr = "Accept terms of services before submit.";
} else {
$agree = input_data($_POST["agree"]);
}
}
function input_data($data) {
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
?>
<h2>Registration Form</h2>
<span class = "error">* required field </span>
<br><br>
<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]); ?>" >
Name:
<input type="text" name="name">
<span class="error">* <?php echo $nameErr; ?> </span>
<br><br>
E-mail:
<input type="text" name="email">
<span class="error">* <?php echo $emailErr; ?> </span>
<br><br>
Mobile No:
<input type="text" name="mobileno">
<span class="error">* <?php echo $mobilenoErr; ?> </span>
<br><br>
Website:
<input type="text" name="website">
<span class="error"><?php echo $websiteErr; ?> </span>
<br><br>
Gender:
<input type="radio" name="gender" value="male"> Male
<input type="radio" name="gender" value="female"> Female
<input type="radio" name="gender" value="other"> Other
<span class="error">* <?php echo $genderErr; ?> </span>
<br><br>
Agree to Terms of Service:
<input type="checkbox" name="agree">
<span class="error">* <?php echo $agreeErr; ?> </span>
<br><br>
<input type="submit" name="submit" value="Submit">
<br><br>
</form>
<?php
if(isset($_POST['submit'])) {
if($nameErr == "" && $emailErr == "" && $mobilenoErr == "" && $genderErr == "" && $websiteErr == "" && $agreeErr == "") {
echo "<h3 color = #FF0001> <b>You have sucessfully registered.</b> </h3>";
echo "<h2>Your Input:</h2>";
echo "Name: " .$name;
echo "<br>";
echo "Email: " .$email;
echo "<br>";
echo "Mobile No: " .$mobileno;
echo "<br>";
echo "Website: " .$website;
echo "<br>";
echo "Gender: " .$gender;
} else {
echo "<h3> <b>You didn't filled up the form correctly.</b> </h3>";
}
}
?>
</body>
</html>
