Pre-select drop-down item by value

pre-select.php

<?php
function preselect_option() {

// URL should be in the format https://xxxxxxx/?option=VALUE_OF_OPTION
$option = htmlspecialchars($_GET["option"]);

echo '<script>';
echo 'function setSelectedIndex(s, valsearch) {';
echo '  // Loop through all the items in drop down list';
echo '  for (i = 0; i< s.options.length; i++) { ';
echo '    if (s.options[i].value == valsearch) {';
echo '      // Item is found. Set its property and exit';
echo '      s.options[i].selected = true;';
echo '      break;';
echo '    }';
echo '  }';
echo '  return;';
echo '}';
echo 'setSelectedIndex(document.getElementById("pa_plan"),"' . $option . '");';
echo '</script>';
}

add_action('wp_footer', 'preselect_option');

?>