Can you add placerholders for this plugin please ?
Exemple:
a placeholder for count how player online use 1.8 or 1.9 PVP (with /ocm toggle)
a placeholder for display wich pvp a player use (or me)

Ok nice ^^

I'm not sure about the first placeholder, since I feel like it might be resource intensive to go through all players and see how many are using 1.9+ PvP and how many aren't. But I could definitely add a placeholder for your current PvP mode.

Please try the latest development build and let me know how it works for you. The placeholder is %ocm_pvp_mode%.

Downloaded and tested, it's not work :/

Are you sure (1) PlaceholderAPI is installed, (2) you removed the old version of OldCombatMechanics, (3) you restarted your server, and (4) you used %ocm_pvp_mode% as the placeholder?

Yes I have do all of these things

Can you send me your latest server log file so I can check for errors?