signature – Locally Sign transactions Blockcypher API

I’m having a problem that I can’t solve since yesterday with the blockCypher APIs when I try to create a new transaction and submit it.

https://www.blockcypher.com/dev/bitcoin/?shell#creating-transactions

i have to sign locally but their php or cURL code don’t work (they give me several problems)

I searched the internet but found nothing suitable.
many signing tools found online tell me to enter a message in addition to the private key, what message should I enter? does not refer to any messages here:

# next, you sign the data returned in the tosign array locally
# any ECDSA secp256k1 signing tool should work
# $PRIVATEKEY here is a hex-encoded private key corresponding to the input from address 
CEztKBAYNoUEEaPYbkyFeXC5v8Jz9RoZH9

sign: 32b5ea64c253b6b466366647458cfd60de9cd29d7dc542293aa0b8b7300cd827 $PRIVATEKEY

3045022100921fc36b911094280f07d8504a80fbab9b823a25f102e2bc69b14bcd369dfc7902200d07067d47f040e724b556e5bc3061af132d5a47bd96e901429d53c41e0f8cca

do you have any algorithm that i can use in php?