if include in array php code example

Example 1: check null in_array php

if (!empty($data_days) && in_array(1, $data_days, true)){ // use numeric value 1, not string

Example 2: what is use of in_array() function in php

The in_array() function is an inbuilt function in PHP. 
The in_array() function is used to check whether a given value exists in an array or not.
It returns TRUE if the given value is found in the given array, and FALSE otherwise.

  <?php
  
$people = array("Peter", "Joe", "Glenn", "Cleveland");

if (in_array("Glenn", $people))
  {
  echo "Match found";
  }
else
  {
  echo "Match not found";
  }

?>