文件上次修改日期不正确

I have a function that displays a list of all the files upload to a specific webpage. I also want to display the date that the file was last modified, but it is displaying all of the dates as December 31 1969 19:00:00. How do I amend this function so that it displays the correct date? (it's in the echo statement at the end):

<?php     
    foreach($phpfiles as $phpfile)
    {
        $imageFileType = pathinfo($phpfile,PATHINFO_EXTENSION);
        if ($imageFileType == "pdf") {
            $faicon = 'fa fa-file-pdf-o'; 
        } else if ($imageFileType == "doc" || $imageFileType == "docx") {
            $faicon = 'fa fa-file-word-o'; 
        } else if ($imageFileType == "xls" || $imageFileType == "xlsx") {
            $faicon = 'fa fa-file-excel-o'; 
        } else if ($imageFileType == "ppt" || $imageFileType == "pptx") {
            $faicon = 'fa fa-file-powerpoint-o'; 
        } else if ($imageFileType == "mp4") {
            $faicon = 'fa fa-file-video-o'; 
        } else if ($imageFileType == "jpg" || $imageFileType == "png" || $imageFileType == "gif" || $imageFileType == "bmp") {
            $faicon = 'fa fa-file-image-o'; 
        } else {
            $faicon = 'fa fa-file-text-o'; 
        }
        if ($server_name <> ""){ 
            $phpfile = "http://". $server_name . '/' .$phpfile;
        }
        echo "<span class='$faicon w3-large'></span>&emsp;&emsp;<a href='$phpfile' class='w3-medium' target='_blank'>".substr(basename($phpfile),-1*strlen(basename($phpfile))+strlen($id)+1)."</a>&nbsp;". date("F d Y H:i:s.", filemtime($phpfile));
    }
?>

As in comments above:

The problem is that you overwrite the variable $phpfile with this code:

if ($server_name <> ""){ 
    $phpfile = "http://". $server_name . '/' .$phpfile;
}

If you instead create a variable with the filemtime date before you change string $phpfile then you can echo it later.

$date = date("F d Y H:i:s.", filemtime($phpfile));
if ($server_name <> ""){ 
    $phpfile = "http://". $server_name . '/' .$phpfile;
}
echo "<span class='$faicon w3-large'></span>&emsp;&emsp;<a href='$phpfile' class='w3-medium' target='_blank'>".substr(basename($phpfile),-1*strlen(basename($phpfile))+strlen($id)+1)."</a>&nbsp;". $date;