PHP search query results not showing apostrophes

Running a simple search query, which feeds into an android studio textview. When I first managed to display results via .php site, all special characters ([{]}) were on show, but i added this line to remove:

echo json_encode($resultArray, DEFINED('JSON_INVALID_UTF8_IGNORE') ? JSON_INVALID_UTF8_IGNORE : 0);

However, this now means that the results that show are also missing special characters, mainly " ' ". So "You're", is actually showing "Youre".

I have tried to play with the above json query, but with no luck - any idea what I'm doing wrong?

Full code for clarity:

<?php

 // Create connection
$con=mysqli_connect("server","user","pass","table");
 
// Check connection
if (mysqli_connect_errno())
{
    echo "Failed to connect to MySQL: " . mysqli_connect_error();
}
 
// Select all of our stocks from table 'stock_tracker'
$sql = "
SELECT Task_title
     , task_description
  FROM TASKS
 ORDER 
    BY RAND () ASC 
 LIMIT 1
";
 
// Confirm there are results
if ($result = mysqli_query($con, $sql))
{
    // We have results, create an array to hold the results
    // and an array to hold the data
    $resultArray = array();
    $tempArray = array();
 
    // Loop through each result
    while($row = $result->fetch_object())
    {
        // Add each result into the results array
        $tempArray = $row;
        array_push($resultArray, $tempArray);
    }
 
    // Encode the array to JSON and output the results

echo json_encode($resultArray, DEFINED('JSON_INVALID_UTF8_IGNORE') ? JSON_INVALID_UTF8_IGNORE : 0);
    
    echo json_last_error_msg(); // Print out the error if any
die(); // halt the script
}
 
// Close connections
mysqli_close($con);
?>