<?php
 
function strtolowertr($metin){ 
    return mb_convert_case(str_replace('I','ı',$metin), MB_CASE_LOWER, "UTF-8"); 
} 
function strtouppertr($metin){ 
    return mb_convert_case(str_replace('i','İ',$metin), MB_CASE_UPPER, "UTF-8"); 
} 
function ucfirsttr($metin) { 
    $metin = in_array(crc32($metin[0]),array(1309403428, -797999993, 957143474)) ? array(strtouppertr(substr($metin,0,2)),substr($metin,2)) : array(strtouppertr($metin[0]),substr($metin,1)); 
return $metin[0].$metin[1]; 
} 
 
$s = "this is the, sample text.for replace the each words in, this'text sample' words";
echo preg_replace_callback('~\b\w+~u', function ($m) { return ucfirsttr($m[0]); }, $s);
 

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