Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/IOFactory.php
public static function identify($pFilename)
    {
        $reader = self::createReaderForFile($pFilename);
        $className = get_class($reader);
        $classType = explode('\\', $className);
        unset($reader);

        return array_pop($classType);
    }
public static function identify($pFilename)
    {
        $reader = self::createReaderForFile($pFilename);
        $className = get_class($reader);
        $classType = explode('\\', $className);
        unset($reader);

        return array_pop($classType);
    }
Identify file type using automatic Reader\IReader resolution.

@param string $pFilename The name of the spreadsheet file to identify

@throws Reader\Exception

@return string