PHP – Validate Name
The code below demonstrates a straightforward method to validate whether the name field contains only letters, dashes, apostrophes, and whitespaces. If the name field’s value is not valid, an error message is stored:
$name = test_input($_POST["name"]);
(!preg_match("/^[a-zA-Z-' ]*$/",$name)) {
$nameErr = "Only letters and white space allowed";
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| The preg_match() function searches a string for a pattern and returns true if the pattern is found, otherwise false. |
PHP – Validate E-mail
The simplest and safest method to validate if an email address is well-formed is by using PHP’s filter_var() function.
In the code below, if the email address is not well-formed, an error message is stored:
$email = test_input($_POST["email"]);
(!filter_var($email, FILTER_VALIDATE_EMAIL)) {
$emailErr = "Invalid email format";
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PHP – Validate URL
The code below demonstrates how to validate a URL address syntax (allowing dashes in the URL). If the URL address syntax is invalid, an error message is stored:
$website = test_input($_POST["website"]);
(!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$website)) {
$websiteErr = "Invalid URL";
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PHP – Validate Name, E-mail, and URL
The script now looks like this:
Example
// define variables and set to empty value
$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"]);
// check if name only contains letters and whitespace
if (!preg_match("/^[a-zA-Z-' ]*$/",$name)) {
$nameErr = "Only letters and white space allowed";
}
}
if (empty($_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"]);
// check if URL address syntax is valid (this regular expression also allows dashes in the URL)
if (!preg_match("/\b(?:(?:https?|ftp):\/\/|www\.)[-a-z0-9+&@#\/%?=~_|!:,.;]*[-a-z0-9+&@#\/%=~_|]/i",$website)) {
$websiteErr = "Invalid URL";
}
}
if (empty($_POST["comment"])) {
$comment = "";
} else {
$comment = test_input($_POST["comment"]);
}
if (empty($_POST["gender"])) {
$genderErr = "Gender is required";
} else {
$gender = test_input($_POST["gender"]);
}
}
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The next step is to demonstrate how to prevent the form from clearing all input fields when the user submits the form.
