PHP - 更清洁，更优雅的方式来验证表单的内容

I am currently working on a Upload page, where users enter in values to forms then click submit. I am going to check to see if the forms have been submitted, and if submitted that they weren't empty. Here is my current code

function validPost()
{
    if(isset($_POST["title"]) && //if a post has been submitted
       isset($_POST["artist"]) &&
       isset($_POST["genre"]) &&
       isset($_POST["url"]) &&
       isset($_POST["user"]) ) 
    { 
        if (strlen($_POST['title']) <= 0) {
            echo 'ERROR: Please enter a title. </ br>';
            return false;
        }
        else if (strlen($_POST['artist']) <= 0) {
            echo 'ERROR: Please enter an artist. </ br>';
            return false;
        }
        else if (strlen($_POST['genre']) <= 0) {
            echo 'ERROR: Please select a genre. </ br>';
            return false;
        }
        else if (strlen($_POST['url']) <= 0) {
            echo 'ERROR: Please enter a url. </ br>';
            return false;
        }
        else if (strlen($_POST['user']) <= 0) {
            echo 'ERROR: Please enter a username to submit the song (or make one up). </ br>';
            return false;
        }
        else
            return true;
    }
    else //if no post was submitted
    { 
        return false;
    }
}

Is there a more elegant way to check this? I plan on adding more checks in the future to the content submitted by these forms and I feel like this is a sloppy way to do it.

Thanks!

Assuming that all of the fields will be check for non-zero string lengths only:

$field_checks = array(
//   'fieldname' => 'errormessage'
   'title' => 'Please enter a title',
   'url' => 'Please enter a URL',
   etc...
);

$errors = array();    
foreach ($field_checks as $field => $errmsg) {       
    if (!isset($_POST[$field]) || ($_POST[$field] === '')) {
        $errors[] = $errmsg;
    }
}

if (count($errors) > 0) {
     print_r($errors); // probably want a nicer error display than this
     return false;
}

Check into jQuery and the validate plugin