Allow only capital and small letters

Question

I would like to accept only small and capital letters from the user.

I tried the below code, it echoes the invalid character message but doesn't work. I mean it doesn't check. It just displays the message. Any help?

<form action="" method="post">
<input type="text" name="fname">
<input type="submit" value="Send" name="submit">
</form>

Update: this is what I have to check and insert the name to database. if numbers found in the name reject the name by displaying the error message else if the name contains only letters insert it into database. That's all I want to acheive.

<?php
if ( isset( $_POST['submit'] ) ) { 
$fname = $_POST["fname"];

if(!preg_match ('/^([a-zA-Z]+)$/', $fname)){
echo "Invalid characters";
}

if (empty($fname)) {
echo  '<span> First name is required</span>';
}

else{
$mysqli = new mysqli("localhost", "root", "", "test");
$stmt = $mysqli->prepare("INSERT INTO test (firstname) VALUES (?)");

$stmt->bind_param("s", $fname);
$stmt->execute();

$stmt->close();

$mysqli->close();


}
}
?>

Answer 1

If you just want to check you could use ctype_alpha() but you said you want to ACCEPT only letters so if you choose to accept the input you could:

$fname=preg_replace('/[^a-z]/i','',$fname);

better after the check

Answer 2

if(!isset($_POST['fname']) || !ctype_alpha($_POST['fname'])){
  // can i haz alpha letters only?
}

(reference)

Answer 3

There are several issues with the code, and the one you are stuck with is probably that you have the form and its processing in the same PHP file. That’s possible, but it requires a different approach. For a starter, it’s probably better to separate them.

What happens with the code posted is that the PHP processor tries to process the form data when no form has been submitted, without even checking for the presence of the data. Now $fname is undefined, so the test always fails.

The test is wrong, too. Now it only checks whether $fname contains at least one letter. For example, if(!preg_match ('/^[a-zA-Z]+$/', $fname)) would test that $fname consists of one or more Ascii letters and nothing else.