title: How to get all values from one array which do not exist in another array?
body: <p>How to get the values from an array that are NOT in another array in PHP?</p>
  
  <p>My current aproach have bad time complexity. Is there an inbuilt php function that can solve my problem?</p>
  
  <p>Example:</p>
  
  <pre><code>$a1 = array(1,2,3,4);
  $a2 = array(3,4,5,6,7);
  </code></pre>
  
  <p>Result:</p>
  
  <pre><code>[5,6,7];
  </code></pre>