在 PHP 脚本运行时添加加载图像

我有一个PHP脚本（粘贴在下面），它从URL列表中提取元数据，问题是加载可能需要一段时间，用户永远不知道何时完全完成（除非他们关注浏览器选项卡中的加载图标）

我已经在网上寻找了很长时间，但找不到解决方案，我已经阅读了我可以使用 Ajax，但我究竟如何在这个脚本上使用它？

感谢您的帮助！

<script type="text/javascript">
function showContent(vThis)
{
    // http://www.javascriptjunkie.com
    // alert(vSibling.className + " " + vDef_Key);
    vParent = vThis.parentNode;
    vSibling = vParent.nextSibling;
    while (vSibling.nodeType==3) { // Fix for Mozilla/FireFox Empty Space becomes a TextNode or         Something
        vSibling = vSibling.nextSibling;
    };
    if(vSibling.style.display == "none")
    {
        vThis.src="collapse.gif";
        vThis.alt = "Hide Div";
        vSibling.style.display = "block";
    } else {
        vSibling.style.display = "none";
        vThis.src="expand.gif";
        vThis.alt = "Show Div";
    }
    return;
}
</script>

<form method="POST" action=<?php echo "'".$_SERVER['PHP_SELF']."'";?> >
<textarea name="siteurl" rows="10" cols="50">
<?php //Check if the form has already been submitted and if this is the case, display the   submitted content. If not, display 'http://'.
echo (isset($_POST['siteurl']))?htmlspecialchars($_POST['siteurl']):"http://";?>
</textarea><br>
<input type="submit" value="Submit">
</form>
</div>
<div id="nofloat"></div>
<div style="margin-top:5px;">
<h4><img src="expand.gif" alt="Show Div" border="0" style="margin-right:6px; margin-  top:3px; margin-bottom:-3px; cursor:pointer;" onclick="showContent(this);" />Show me the    script working!</h4>
<div style="margin-top:5px; display:none;">
<table class="metadata" id="metatable_1">
<?php
ini_set('display_errors', 0);
ini_set( 'default_charset', 'UTF-8' );
error_reporting(E_ALL);
//ini_set( "display_errors", 0);
function parseUrl($url){
    //Trim whitespace of the url to ensure proper checking.
    $url = trim($url);
    //Check if a protocol is specified at the beginning of the url. If it's not,     prepend 'http://'.
    if (!preg_match("~^(?:f|ht)tps?://~i", $url)) {
            $url = "http://" . $url;
    }
    //Check if '/' is present at the end of the url. If not, append '/'.
    if (substr($url, -1)!=="/"){
            $url .= "/";
    }
    //Return the processed url.
    return $url;
}
//If the form was submitted
if(isset($_POST['siteurl'])){
    //Put every new line as a new entry in the array
    $urls = explode("'n",trim($_POST["siteurl"]));
    //Iterate through urls
    foreach ($urls as $url) {
            //Parse the url to add 'http://' at the beginning or '/' at the end if not   already there, to avoid errors with the get_meta_tags function
            $url = parseUrl($url);
            //Get the meta data for each url
            $tags = get_meta_tags($url);
            //Check to see if the description tag was present and adjust output    accordingly
            $tags = NULL;
$tags = get_meta_tags($url);
if($tags)
echo "<tr><td>$url</td><td>" .$tags['description']. "</td></tr>";
else 
echo "<tr><td>$url</td><td>No Meta Description</td></tr>";
    }
}
?>
</table>
</div>
<script type="text/javascript">
        var exportTable1=new ExportHTMLTable('metatable_1');
    </script>
<div>
        <input type="button" onclick="exportTable1.exportToCSV()"   value="Export to CSV"/>
        <input type="button" onclick="exportTable1.exportToXML()"   value="Export to XML"/>
    </div>
</div>