Просмотр поста

<?php
/**
 * @param string $filename
 *
 * @return bool|string
 */
function isImage($filename)
{
    if (
        file_exists($filename) &&
        in_array(
            $mime_type = (new finfo(FILEINFO_MIME_TYPE))->file($filename),
            ['image/gif', 'image/jpeg', 'image/png']
        )
    ) {
        return $mime_type;
    }

    return false;
}

var_dump(
    isImage('lol.png'),
    isImage('a.jpg'),
    isImage('a2.gif'),
    isImage(''),
    isImage(__FILE__)
);