如何启动“提交”按钮功能

I'm currently developing a form for web scraping activities, how can i initiate the submit button function using isSet?

here's my code:

<form id="startWeb" name="startWeb" method="post" action="webcrawlBM_process.php">
<input type="button" id="startCrawl" action="submit" value="Mula Mengikis" class="gradient-background" onClick="submitForm();" style="width: 230px" />

when the user clicks on submit, a javascript function will initiate.

function submitForm(action)
{
    document.getElementById('startWeb').action = action;
    document.getElementById('startWeb').submit();
    alert('Data anda telah disimpan!  Anda akan dihalakan kembali ke halaman utama.');
    window.location = 'index.php';
}

here's my isset function that is problematic.

if (isset($_POST['submit'])) { $webcrawl = new WebCrawlerBM($_POST['target_url']);

if ($webcrawl->WebCrawlerBM($_POST['target_url'])) {
if ($webcrawl->submitForm()) {
    $webcrawl->set_webpage($url);
    $webcrawl->set_makefile($text); 
    $webcrawl->set_writefile($filename);
    $webcrawl->set_striphtmltags($text);

    echo "Your action had been completed successfully.  <br>";
} 

The situation is that when i click, nothing happens.