If you have MBA of 90 credit hours plus 2 years Bachelors, your education is 18 years which is equal to MS/Mphil, so you can apply for PHD.

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اللَّهُمَّ إِنِّي أَسْأَلُکَ عِلْمًا نَافِعًا وَرِزْقًا طَيِّبًا وَعَمَلًا مُتَقَبَّلًا