Vendor/phpspreadsheet/phpoffice/phpspreadsheet/src/PhpSpreadsheet/IOFactory.php
public static function createReaderForFile($filename)
    {
        File::assertFile($filename);

        // First, lucky guess by inspecting file extension
        $guessedReader = self::getReaderTypeFromExtension($filename);
        if ($guessedReader !== null) {
            $reader = self::createReader($guessedReader);

            // Let's see if we are lucky
            if (isset($reader) && $reader->canRead($filename)) {
                return $reader;
            }
        }

        // If we reach here then "lucky guess" didn't give any result
        // Try walking through all the options in self::$autoResolveClasses
        foreach (self::$readers as $type => $class) {
            //    Ignore our original guess, we know that won't work
            if ($type !== $guessedReader) {
                $reader = self::createReader($type);
                if ($reader->canRead($filename)) {
                    return $reader;
                }
            }
        }

        throw new Reader\Exception('Unable to identify a reader for this file');
    }
public static function createReaderForFile($filename)
    {
        File::assertFile($filename);

        // First, lucky guess by inspecting file extension
        $guessedReader = self::getReaderTypeFromExtension($filename);
        if ($guessedReader !== null) {
            $reader = self::createReader($guessedReader);

            // Let's see if we are lucky
            if (isset($reader) && $reader->canRead($filename)) {
                return $reader;
            }
        }

        // If we reach here then "lucky guess" didn't give any result
        // Try walking through all the options in self::$autoResolveClasses
        foreach (self::$readers as $type => $class) {
            //    Ignore our original guess, we know that won't work
            if ($type !== $guessedReader) {
                $reader = self::createReader($type);
                if ($reader->canRead($filename)) {
                    return $reader;
                }
            }
        }

        throw new Reader\Exception('Unable to identify a reader for this file');
    }
Create Reader\IReader for file using automatic Reader\IReader resolution.

@param string $filename The name of the spreadsheet file

@throws Reader\Exception

@return Reader\IReader