php -r "command" で可能

root@f1eb1edceb79:/var/www/html# php -r "print_r(gd_info());"
Array
(
    [GD Version] => bundled (2.1.0 compatible)
    [FreeType Support] =>
    [GIF Read Support] => 1
    [GIF Create Support] => 1
    [JPEG Support] =>
    [PNG Support] => 1
    [WBMP Support] => 1
    [XPM Support] =>
    [XBM Support] => 1
    [WebP Support] => 1
    [BMP Support] => 1
    [JIS-mapped Japanese Font Support] =>
)