php is sending invalid email address - php

Question

Hello after 3 days of trying to put my form together, I have come across a problem...
Using the form, It can validate when i press submit. which is good, but once i press send, the invalid data still gets sent to my inbox.. so I will end up with two emails.. one with invalid data and then one with the valid data which is typed in after the error messages have been displayed and re-sent. If anyone can look at my code and see what I am missing, or have done wrong i will appreciate it soo much
<?php
if (isset($_POST['submit'])) {
//check email
if(empty($_POST['email_addr']))
$msg_email = "*";
$email_subject = $_POST['email_addr'];
$email_pattern = '/^\w+([\.-]?\w+)*#\w+([\.-]?\w+)*(\.\w{2,3})+$/';
preg_match($email_pattern, $email_subject, $email_matches);
if(!$email_matches[0])
$msg2_email = "Please enter a valid email address";
}
// validation complete
if(isset($_POST['submit'])){
if($msg_name=="" && $msg2_name=="" && $msg_email=="" && $msg2_email=="")
$msg_success = "Thankyou for your enquiry";
//send mail
$EmailFrom = "someone#somewhere.com";
$EmailTo = "someone#somewhere.com";
$Subject = "Online contact form";
$email_addr = Trim(stripslashes($_POST['email_addr']));
}
// prepare email body text
$Body = "";
$Body .= "email_addr: ";
$Body .= $email_addr;
$Body .= "\n";
// send email
$success = mail($EmailTo, $Subject, $Body, "From: $EmailFrom");
?>

Answer 1

I would not use your regular expression to validate email addresses. I'd use filter_var instead.
if( !filter_var($_POST['email_addr'], FILTER_VALIDATE_EMAIL) ) {
$msg2_email = "Please enter a valid email address";
}
filter_var returns false if the filter fails, otherwise it returns the filtered email address.
On top of that, you can set a default value if your filter fails. For example, suppose that the email address field is not necessary, so instead writing yet another line of code to check for null-ness in your variables like:
$isEmailNull = ( $_POST['email_addr'] === NULL) ? NULL : $_POST['email_addr'];
with filter_var you can write it like:
$emailAddress = filter_var( $_POST['email_addr'], FILTER_VALIDATE_EMAIL,
array('options' => array(
'default' => null
)
));
If your filter fails, then $emailAddress is not false, but null. Which makes more sense for non-boolean variables.
You can read more about filter_var here
you can validate/sanitize IP addresses, URLs, Email addresses, ASCII characters, numbers, etc... without using regular expressions that may or may not work.