әәә..әә.әәәә.әәәәәәәә.ә.әәәәә.әәә
әәә.
.әә.
әәәә
.әәә
әәәә
ә.ә.
әәәә
ә.әә
ә

Array ( [0] => 1 [1] => а [2] => 2 [3] => б [4] => 3 [5] => в )
Array ( [0] => 1а [1] => 2б [2] => 3в )

test with short strings

saved result:
б3в; 0.691648960114 (convert)
б3в; 0.0993728637695 (mb_substr)
б3в; 0.170913934708 (array_chunk)
б3в; 0.484570980072 (convert2)
б3в; 0.550544977188 (convert3)


test with a long string

saved result:
б3в; 0.118468999863
б3в; 0.731743097305
б3в; 0.101760149002
б3в; 0.126809120178
б3в; 0.141029119492