Soldiers in the middle are archers and onager units. Soldiers on the circumference of the circle are hoplite units.
Couple of thoughts on that.
The biggest problem is that the formation has little to no tactical mobility. To try to move field artillery of any size, along with ammo for it, and expect the men to face all directions and move is ridiculous under battlefield conditions.
That is a huge target. If your archers are aiming for the middle and under shoot, or over shoot, or are off to the left or right they will still be on target.
It is incredibly inflexible. You had better hope you are in a position that the enemy HAS to attack you, and that they cant just wait until you run out of food and water, or simply move around you.
In different eras through history you would see combined arms formations on the battlefield, such as the Spanish Squares but that was meant to give tactical flexibility, not remove it.
It seems broadly similar to the Napoleonic Square or the Laager, both of which are effective only against an enemy over whom you have an overwhelming superiority in ranged weaponry.
The square was a defence against cavalry - who had no ranged weapons - but was quite useless against anything else. They worked at Waterloo because Ney, in his haste, and possible PTSD, neglected to bring forward his horse artillery which would have chewed its way through the squares in no time. The squares would have been quite useless against infantry as well as you are minimising, rather than maximising your effective fire power, 75% of which is going to be facing the wrong way.
Similarly the British used a Napoleonic style square at Ulundi and defeated the Zulus by sheer weight of firepower, as was the case at Blood-River (although I suspect the story of Blood River as told to fit the Afrikaaner nationalist narrative a pile of old cobblers).
On the other hand, when you do not have an overwhelming superiority in ranged weapons, its a suicidal thing to do. Cronje did this at Paardeberg and sealed his fate. The British 'Boxes' at Gazala were similarly dangerous, being ready made traps from which escape was by no means certain.
Effectively you are Cannae'ing yourself.
You are offering the enemy - on a silver platter - his wet dream of an encirclement by arranging yourself into a nice neat kettle ready for to be annihilated at his leisure.
