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<?php $que = 'bbb ahhj aaab cc iiik xxx fjjj baaaaaab yyyaaa'; echo preg_replace("/\\b([a-z])\\1+(?!\\1|\\b)|(?<=([a-z]))((?!\\2)[a-z])\\3+/","$1$3",$que);
Output for 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
bbb ahj ab cc ik xxx fj bab ya

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