<?php

error_reporting(-1);
mb_internal_encoding('utf-8');

$text = '             привет.есть 2 функции,preg_split и explode ,не понимаю,в чем между ними разница.        васса,это борода.';

function makeFirstLetterUppercase($text) {
	$parts = preg_split('/(?<=[.!?])/u', $text, 0, PREG_SPLIT_NO_EMPTY);
	$result = '';
		foreach($parts as $key => $sentence) {
			$sentence = trim($sentence);
			$otherPart = mb_substr($sentence, 1);
			$firstLetter = mb_strtoupper(mb_substr($sentence, 0, 1));
			$result = $firstLetter . $otherPart;
		}
	return $result;
}

function fixText($text) {
	$regexpTooManySpaces = '/\\s*([.,!?;])\\s*/';
	$result = preg_replace($regexpTooManySpaces, '$1 ', $text);
	return $result;
}
//echo makeFirstLetterUppercase($text);
$text = makeFirstLetterUppercase($text);
$text = fixText($text);
echo $text;