modify key in a foreach loop php - php

Question

I want to change the value of the $key because I have array_splice inside the loop which change the position of my values so - it mess up the value I need in a specific place.
I tried $key-- but it doesn't work.
for example when I print the $key after I do echo $key it's fine but when I echo $key just after the foreach loop I get the worng value.
Any ideas?
foreach ($cut as $key => $value) {
echo "foreach key:".$key."<br>";
if(in_array($value,$operators))
{
if($value == '||')
{
echo "found || in position:".$key."<br>";
if(($key+1<sizeof($cut)))
{
$multi = new multi;
echo "<br>"."key-1: ";
print_r($cut[$key-1]);
echo"<br>";
echo "<br>"."key+1: ";
print_r($cut[$key+1]);
echo"<br>";
$res = $multi->orex($cut[$key-1],$cut[$key+1],$numString);
$cut[$key-1]= $res;
array_splice($cut,$key,1);
array_splice($cut,$key,1);
$key--; //here trying to change the key
echo "new string:";
print_r($cut);
echo "<br>";
echo "key:".$key."<br>";
}
}
}
}

Answer 1

Updated
I don't think it is a good idea to change the array itself inside the foreach loop. So please crete another array and fill data into it, which will be your result array. This method works well when your array data is not big, in other words, most situations.
Origin
I don't know what do you mean. Let me give it a guess...
You want:
foreach($arr as $key=>$val){
$newkey = /* what new key do you want? */
$arr[$newkey] = $arr[$key];
unset($arr[$key]);
}