Is comparing similarity of values of two arrays possible?

Question

string of the first array$arr_prim[] shall be null when it is similar to the second $arr_sec[] ,

 <?php
    $arr_prim[] = array('2','3');

 //array primaria

    $arr_sec[] = array('1','2','3');

  //array secundaria


   foreach($arr_prim as & $key):
     var_dump($key); 
   endforeach;

   foreach($arr_sec as & $res):
   var_dump($res);
   endforeach; 
   ?>
      /*Ambos irá imprimir 
   array (size=3)
  0 => string '1' (length=1)
  1 => string '2' (length=1)
  2 => string '3' (length=1)
   */     

   foreach($arr_prim as $k => $value){
        if($s = array_search($value, $arr_sec)){

        $arr_sec[$k] = null;
        var_dump($arr_sec);

    /*resultado da impressão:
    array (size=3)
        0 => null
        1 => string '2' (length=1)
        2 => string '3' (length=1)
    */

        }

    }

Answer 1

The question lacks more details.

Regardless of that I made a simple repetition loop where it checks if the value of one array exists in the other:

$arr_prim = array('1','2','3');
$arr_sec = array('2','3');

foreach ($arr_sec as $k => $v) {
    if ($p = array_search($v, $arr_prim)) {
        echo 'encontrou valor '.$v.' no array primário, na posição '.$p.PHP_EOL.'<br>';
        /*
        Setar valor nulo?
        quem deve receber valor nulo? array primario ou secundario? o array inteiro ou somente a posição onde foi encontrado?
        Se a poição não existir, deve ser criada e setada como nulo?
        */

        $arr_prim[$k] = null;
    }
}

ex if the number 2.3 of the first array is similar to the 2.3 of the second array, I want it to be null

In this section it is not clear whether you are talking about positions/indexes/keys or values. Example,

The primary and secondary array have value 2 and 3. This means that the primary array should look like this:

array(1, null, null)

Another way of interpreting the question is based on indexes and not only on values. But I’d rather not write more code until it’s clear what needs to be done.