$original_filename = explode('_', $list->file);
$timestamp         = array_shift($original_filename);
$original_filename = implode('_', $original_filename);

$original_filename = ltrim(stristr($list->file, '_'), '_');

$original_filename = '1347020478_Workbook1 12.19.19.csv';
echo substr( $original_filename, strpos( $original_filename, '_') + 1);

$loops=1000000;

$filename="1347020478_Workbook1 12.19.19.csv";
for ($i=0;$i<$loops;$i++){
    $fn[$i]=$filename;
}

$start1=time();
for ($i=0;$i<$loops;$i++){
    $newname=substr($fn[$i],11);
}
$end1=time();
echo $newname." time=".($end1-$start1)."<br><br>";


$filename="1347020478_Workbook1 12.19.19.csv";
for ($i=0;$i<$loops;$i++){
    $fn[$i]=$filename;
}

$start1=time();
for ($i=0;$i<$loops;$i++){
    $original_filename  = explode('_', $fn[$i]);
    $timestamp          = array_shift($original_filename);
    $original_filename  = implode('_', $original_filename);
}
$end1=time();
echo $original_filename." time=".($end1-$start1)."<br><br>";


$filename="1347020478_Workbook1 12.19.19.csv";
for ($i=0;$i<$loops;$i++){
    $fn[$i]=$filename;
}

$start1=time();
for ($i=0;$i<$loops;$i++){
    $st=strpos($fn[$i],"_");
    $newname=substr($fn[$i],$st+1);
}
$end1=time();
echo $newname." time=".($end1-$start1);

$original_filename = substr($list->file, 11);

preg_replace('/^[0-9]+_/', '', $filename);