Fonction modification chaine de caractère php

<?php
function str_replace_all($search,$replace,$subject) {
  while(strpos($subject,$search)!==false) {
    $subject = str_replace($search,$replace,$subject);
  }
  return $subject;
}
  
function remplace($chaine,$arg1,$arg2,$motif){
$a=str_replace_all($arg1,$motif,$chaine);
$a=str_replace_all($arg2,$motif,$a);
return $a;
}

echo str_replace_all("titi","????","toto tata tata titi tutu toitoi tototutu").'<br />';
echo remplace("toto tata tata titi tutu toitoi tototutu","toto","titi","????");
?>

<?php
function str_replace_all($search,$replace,$subject) {
  while(strpos($subject,$search)!==false) {
    $subject = str_replace($search,$replace,$subject);
  }
  return $subject;
}
  
function remplace($chaine,$arg1,$arg2,$motif1,$motif2){
$a=str_replace_all($arg1,$motif1,$chaine);
$a=str_replace_all($arg2,$motif2,$a);
return $a;
}

echo str_replace_all("titi","????","toto tata tata titi tutu toitoi tototutu").'<br />';
echo remplace("toto tata tata titi tutu toitoi tototutu","toto","titi","????","xxx");
?>

<?php

$str = 'Lorem ipsum dolor sit amet, consectetur adipisicing elit.';

$res = str_replace(array('et', 'it'), array('ET', 'IT'), $str);
var_dump($res);

$res = strtr($str, array('or' => 'OR', 'ct' => 'CT'));
var_dump($res);

?>

-> php toto.php
string(57) "Lorem ipsum dolor sIT amET, consectETur adipisicing elIT."
string(57) "LORem ipsum dolOR sit amet, conseCTetur adipisicing elit."