/* カーソルでなぞった文字反転 */
function custom_admin_selection_style() {
    echo '<style>
        ::selection {
            background: #3399ff !important;
            color: white !important;
        }
    </style>';
}
add_action('admin_head', 'custom_admin_selection_style');<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /usr/home/hbv10033b5hj/html/blog/wp-content/themes/fcblog/functions.php:42) in <b>/usr/home/hbv10033b5hj/html/blog/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1775</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /usr/home/hbv10033b5hj/html/blog/wp-content/themes/fcblog/functions.php:42) in <b>/usr/home/hbv10033b5hj/html/blog/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1775</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /usr/home/hbv10033b5hj/html/blog/wp-content/themes/fcblog/functions.php:42) in <b>/usr/home/hbv10033b5hj/html/blog/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1775</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /usr/home/hbv10033b5hj/html/blog/wp-content/themes/fcblog/functions.php:42) in <b>/usr/home/hbv10033b5hj/html/blog/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1775</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /usr/home/hbv10033b5hj/html/blog/wp-content/themes/fcblog/functions.php:42) in <b>/usr/home/hbv10033b5hj/html/blog/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1775</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /usr/home/hbv10033b5hj/html/blog/wp-content/themes/fcblog/functions.php:42) in <b>/usr/home/hbv10033b5hj/html/blog/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1775</b><br />
<br />
<b>Warning</b>:  Cannot modify header information - headers already sent by (output started at /usr/home/hbv10033b5hj/html/blog/wp-content/themes/fcblog/functions.php:42) in <b>/usr/home/hbv10033b5hj/html/blog/wp-includes/rest-api/class-wp-rest-server.php</b> on line <b>1775</b><br />
{"code":"rest_missing_callback_param","message":"\u30d1\u30e9\u30e1\u30fc\u30bf\u4e0d\u8db3: url","data":{"status":400,"params":["url"]}}