Validation basically meant for test or check the input values which are submitted by the any user while processing any form or process.
PHP allow us two kind of validation there.
Client-Side Validation These Validation we performed on the client machine.Before sending it to server.
Server Side Validation These validation are take place after submission of data,data sent to a server and validation checks perform not in the client machine ,they perform in the server machine.
Below Example is for required fields validation in a form.
<html>
<head>
<style>
.error {color: #FF0000;}
</style>
</head>
<body>
<?php
// define variables and set to empty values
$nameErr = $emailErr = $genderErr = $websiteErr = "";
$name = $email = $gender = $comment = $website = "";
if ($_SERVER["REQUEST_METHOD"] == "POST") {
if (empty($_POST["name"])) {
$nameErr = "Name is required";
}
else
{
$name = test_input($_POST["name"]);
}
if (empty($_POST["email"])) {
$emailErr = "Email is required";
}
else
{
$email = test_input($_POST["email"]);
// check if e-mail address is well-formed
if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
$emailErr = "Invalid email format";
}
}
if (empty($_POST["website"])) {
$website = "";
}
else
{
$website = test_input($_POST["website"]);
}
if (empty($_POST["comment"])) {
$comment = "";
}
else
{
$comment = test_input($_POST["comment"]);
}
if (empty($_POST["gender"])) {
$genderErr = "Gender is required";
}
else
{
$gender = test_input($_POST["gender"]);
}
}
function test_input($data) {
$data = trim($data);
$data = stripslashes($data);
$data = htmlspecialchars($data);
return $data;
}
?>
<h2>Absolute classes registration</h2>
<p><span class="error">* required field.</span></p>
<form method="post" action="<?php echo htmlspecialchars($_SERVER["PHP_SELF"]);?>">
<table>
<tr>
<td>Name:</td>
<td><input type="text" name="name">
<span class="error">* <?php echo $nameErr;?></span>
</td>
</tr>
<tr>
<td>E-mail:</td>
<td><input type="text" name="email">
<span class="error">* <?php echo $emailErr;?></span>
</td>
</tr>
<tr>
<td>Time:</td>
<td> <input type="text" name="website">
<span class="error"><?php echo $websiteErr;?></span>
</td>
</tr>
<tr>
<td>Classes:</td>
<td> <textarea name="comment" rows="5" cols="40"></textarea></td>
</tr>
<tr>
<td>Gender:</td>
<td>
<input type="radio" name="gender" value="female">Female
<input type="radio" name="gender" value="male">Male
<span class="error">* <?php echo $genderErr;?></span>
</td>
</tr>
<td>
<input type="submit" name="submit" value="Submit">
</td>
</table>
</form>
<?php
echo "<h2>Your given values are as:</h2>";
echo $name;
echo "</br>";
echo $email;
echo "<br>";
echo $website;
echo "<br>";
echo $comment;
echo "<br>";
echo $gender;
?>
</body>
</html>
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