PHP: is there a way to convert a private ECDSA key to its corresponding public key? As described here (https://en.bitcoin.it/wiki/Technical_background_of_version_1_Bitcoin_addresses) I am trying to convert a private ECDSA key to its corresponding public key. (See step1 and step2).

I think I need some code which multiplies some coordinates on the elliptic curve. But I dont know how. Can someone help me, please?

// Unfortunately, this answer doesn't help me enough since I don't understand how to use the code. Can someone clearify that or give alternative solutions? Thanks
Yeah, you do "need some code which multiplies some coordinates on the elliptic curve" :). If you don't have extensive cryptography experience I would recommend you use library rather than trying to implement details yourself.

Googling I've found Bitcoin-lib-php. Looking at  the code it seems it seems this function does exactly what you are looking for.