[WordPress] An example for how to use WP_Query to search for a person by their first name or their last name.

1-name-search.php

<?php

/* First, verify that the hidden field contains the 'true' value. 
 *
 * Note that this field could be controlled by JavaScript such that 
 * if the end user opted to search by something else, then this field 
 * could have a different value and branch to a different conditional.
 */
if ( 'true' == $_POST['member-search-field-searching'] ) {

    /* Read the meta data from the provided fields. The meta key
     * is the first name or last name, the value is the content
     * of the text input field.
     */
    $meta_key   = $_POST['member-search-type'];
    $meta_value = $_POST['member-search-field'];

    // Create an array to store the results of the search
    $users = array();

    // Look for all administrators with the specified name
    $args = array(
        'fields'     => 'all_with_meta',
        'role'       => 'adminsitrator',
        'meta_key'   => $meta_key,
        'meta_value' => $meta_value
    );
    $user_query = new WP_User_Query($args);
    
    // Store the results in the array that was created.
    $users = $user_query->get_results();

}