Front end posting, not working wp_redirect with 'cannot modify header information' error

Question

Im trying to make front end posting page but, sometime 'wp_redirect' is not working with 'cannot modify header information' error. adding data is working well but I don't know why is working well without error sometime, showing error sometime..

Sorry for my bad english, please help me out... and I'm not a programmer just understand some codes anyway...

Many thanks!!

    if (isset ($_POST['post_title'])) {
        $title =  $_POST['post_title'];
    } else {
        echo 'Please enter a game  title';
    }
    if (isset ($_POST['description'])) {
        $description = $_POST['description'];
    } else {
        echo 'Please enter the content';
    }

    $new_post = array(
        'post_title'    => $title,
        'post_content'  => $description,
        'post_status'   => 'publish',
        'post_type' => 'property',  
        'tax_input' => array( 'property_type' => array($property_type), 'suburbs' => array($suburbs) ) 
    );


    //save the new post and return its ID
    $pid = wp_insert_post($new_post); 

       //add thumbnail
        if (!function_exists('wp_generate_attachment_metadata')){
                require_once(ABSPATH . "wp-admin" . '/includes/image.php');
                require_once(ABSPATH . "wp-admin" . '/includes/file.php');
                require_once(ABSPATH . "wp-admin" . '/includes/media.php');
            }
             if ($_FILES) {
                foreach ($_FILES as $file => $array) {
                    if ($_FILES[$file]['error'] !== UPLOAD_ERR_OK) {
                        return "upload error : " . $_FILES[$file]['error'];
                    }
                    $attach_id = media_handle_upload( $file, $pid );
                }   
            }
            if ($attach_id > 0){
                //and if you want to set that image as Post  then use:
                update_post_meta($pid,'_thumbnail_id',$attach_id);
            }  //add thumbnail end

    update_post_meta($new_post_id, 'tax_input', $property_type);
    update_post_meta($new_post_id, 'tax_input', $suburbs);

    //insert custom fields
    update_post_meta($pid,'bathrooms',$_POST['bathrooms']);
    update_post_meta($pid,'property_lease',$_POST['property_lease']);
    update_post_meta($pid,'lost_found_date',$_POST['lost_found_date']);
    update_post_meta($pid,'dog_sex',$_POST['dog_sex']);
    update_post_meta($pid,'latitude',$_POST['latitude']);
    update_post_meta($pid,'longitude',$_POST['longitude']);


    $url = get_permalink( $pid );
    wp_redirect($url);
    exit();
}

 get_header(); 

Answer 1

Lines like this one can cause trouble: if ($_FILES) {. If $_FILES is not set and you try to use it in a conditional like that, you will get a Notice and if debugging is on that notice will print to the screen. I am guessing that is what is happening.

You should check variables with isset or empty, the way you do in a number of other places, and never use a bare variable as if it were a boolean.

Also, you are also returning from what appears to be global scope. When I try that, I get bool(false) printed to the screen. That could cause this issue as well.