ProcessWire front-end upload form example using ProcessWire Inputfields and form processing.

inputfieldfile-form.php

<?php 
/**
 * ProcessWire (2.5) InputfieldFile front-end upload form example
 * Various workarounds to get it working with Errors for WireUpload
 * and removing files upload after error
 */

$sent = false;
$upload_path = $config->uploadTmpDir;

$form = $modules->get("InputfieldForm");
$form->attr("action", "./");
$form->attr("name", "uploadform");

$field = $modules->get("InputfieldFile");
$field->label = "Images";
$field->description = "Upload your images maximal 3 files.";
$field->required = 1;
$field->attr("name+id", 'myimages');
$field->destinationPath = $upload_path;
$field->extensions = "jpg jpeg gif png";
$field->maxFiles = 3;
$field->maxFilesize = 2*1024*1024; // 2mb
$form->add($field);

$field = $modules->get("InputfieldSubmit");
$field->label = "Submit";
$field->attr("name+id",'submit');
$form->add($field);

// if sumbitted process form
if($input->post->submit){

    // process form input
    $form->processInput($input->post);

    // Workaround to get errors from the WireUpload used by the file field
    // Ask Ryan to implement WireUpload errors handling on form file field
    if($form->get("myimages")->getWireUpload()->getErrors()){
        $errors = $form->get("myimages")->getWireUpload()->getErrors();
        foreach($errors as $error) $form->get("myimages")->error($error);
    }

    if(!count($form->getErrors())){
        // if no error occured
        // create new page and save values
        $uploadpage = new Page();
        $uploadpage->template = "upload-entry";
        $uploadpage->parent = $pages->get("/upload-api/");

        // add title/name and make it unique with time and uniqid
        $uploadpage->title = date("d-m-Y H:i:s") . " - " . uniqid();
        $uploadpage->addStatus(Page::statusUnpublished);
        $uploadpage->save();

        // save uploaded files to new page and remove temp files
        $files = explode("|",$form->get("myimages")->value);
        foreach($files as $file){
            if($file && file_exists($upload_path . $file)){
                $uploadpage->myimages->add($upload_path . $file);
                unlink($upload_path . $file);
            }
        }

        $uploadpage->save();
        $sent = true;
        // or better do a redirect here before showing thank you text.

    } else {
        // form incomplete or errors happened
        // we remove files uploaded to temp dir
        $files = explode("|",$form->get("myimages")->value);
        foreach($files as $file){
            if($file && file_exists($upload_path . $file)){
                unlink($upload_path . $file);
            }
        }

        // reset value before rendering the form again to prevent PW errors trying render files (as in admin)
        $form->get("myimages")->value = ''; // reset field value
    }
}

if(!$sent){
    $content .= $form->render();
} else {
    $content .= "<p>Form submission succeded. Thanks!</p>";
    $content .= "<p>Page created: $uploadpage->url</p>";
}

styles.css

.Inputfields,
.Inputfields li {
    list-style: none;
    margin: 1em 0;
    padding: 0;
}

.Inputfields li label {
    font-weight: bold;
}

.Inputfields li p {
    margin: 0;
}

.Inputfields li p.description {
    font-style: italic;
}

.Inputfields textarea,
.Inputfields .InputfieldMaxWidth {
    width: 100%;
}

.Inputfields .InputfieldSubmit label {
    display: none;
}

.ui-state-error-text {
    color: red;
}

/* hide drag upload */
.AjaxUploadDropHere{
    display: none;
}
span.ui-state-error{ color: red;}