title: Array diff problem with one array contains null, and other empty values
body: <p>I am using laravel. I have 2 arrays. For example</p>
  
  <pre><code>$array1 = [
      'test1',
      '',
      'test2',
      'test3',
      '',
      'test4',
      '',
  ];
  
  $array2 = [
      null
  ];
  
  dd(array_diff($array1, $array2));
  </code></pre>
  
  <p>result is </p>
  
  <pre><code>array:4 [▼
    0 =&gt; "test1"
    2 =&gt; "test2"
    3 =&gt; "test3"
    5 =&gt; "test4"
  ]
  </code></pre>
  
  <p>but I expected </p>
  
  <pre><code>array:7 [▼
    0 =&gt; "test1"
    1 =&gt; ""
    2 =&gt; "test2"
    3 =&gt; "test3"
    4 =&gt; ""
    5 =&gt; "test4"
    6 =&gt; ""
  ]
  </code></pre>
  
  <p>Can you ask why in array_diff considered <code>null is equal ''</code>, and how can I fix it without any additional cods. Now I solved this </p>
  
  <pre><code>foreach ($array1 as $key =&gt; $value) {
      if (in_array($value, $array2, true)) {
          unset($array1[$key]);
      }
  }
  </code></pre>