PHP form validation submit problem

Every time I try to submit the form and I have not entered nothing in the year field I get Incorrect year! how can I still submit the form without 开发者_开发问答having to enter a year. In other words leaving the year field blank and not getting a warning?

Here is the PHP code.

if(preg_match('/^\d{4,}$/', $_POST['year'])) {
    $year = mysqli_real_escape_string($mysqli, $_POST['year']);
} else {
    $year = NULL;
}

if($year == NULL) {
    echo '<p class="error">Incorrect year!</p>';
} else {
    //do something
}

if(preg_match('/^\d{4,}$/', $_POST['year'])) {
    $year = mysqli_real_escape_string($mysqli, $_POST['year']);
} else {
    $year = false;
}

if ($year === false) {
    echo '<p class="error">Incorrect year!</p>';
} else {
    //do something
}

OR (if you didn't set YEAR somewhere else)

if(preg_match('/^\d{4,}$/', $_POST['year'])) {
    $year = mysqli_real_escape_string($mysqli, $_POST['year']);
}

if (!isset($year)) {
     echo '<p class="error">Incorrect year!</p>';
} else {
    //do something
}

if(preg_match('/^\d{4,}$/', $_POST['year'])) {
    $year = mysqli_real_escape_string($mysqli, $_POST['year']);
} else if(empty($_POST['year'])){
    $year = '';
} else {
    $year = null;
} 

if($year == NULL) {
    echo '<p class="error">Incorrect year!</p>';
} else {
    //do something
}

Perhaps I'm misunderstanding, but this sounds like what you want.

Hey you can just take this part out and it will take the echo out allowing you to submit with the field being blank

if($year == NULL) {
    echo '<p class="error">Incorrect year!</p>';
} else {
    //do something
}

I wouldn't suggest allowing it to go blank into the database. Maybe you can just grab the default date on the server or a default value meaning the user didn't fill it out. This would take the error out but still leave something in the database field.