<?php
error_reporting(-1);
mb_internal_encoding('utf-8');
 
//$text = "ну что.      не смотрел еще black mesa.я собирался скачать  ,но все как-то некогда было.";
//$text = "roses are red,and violets are blue.whatever you do i'll keep it for you.";
$text = 'привет   .    есть 2 функции  ,  preg_split и explode';
function makeFirstLetterUppercase($text) {
	$partOne = mb_strtoupper(mb_substr($text, 0, 1));
	$partTwo = mb_substr($text,1);
    return $partOne . $partTwo;
}
 
function fixText($text) {
	$arr = preg_split("/(?<=\.)/u", $text, 0, PREG_SPLIT_NO_EMPTY);
	foreach ($arr as &$sent){
		$sent = trim($sent);
		$sent = makeFirstLetterUppercase($sent) ;
	}
	$sent = implode(" ", $arr);
	$sent = preg_replace("/( *([,!?]+))/u", "$2 ", $sent);
	return $sent;
}
$result = fixText($text);
echo $text;
echo "\n";
echo $result;

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