// コンテンツ内のhttpリンクを自動でhttpsに置換する設定
function replace_http_to_https_output($buffer) {
    // 自分のサイトのドメイン（例: http://example.com）をhttpsに置換
    $search_http = 'http://' . $_SERVER['HTTP_HOST'];
    $replace_https = 'https://' . $_SERVER['HTTP_HOST'];
    return str_replace($search_http, $replace_https, $buffer);
}
function start_http_to_https_buffer() {
    ob_start("replace_http_to_https_output");
}
function end_http_to_https_buffer() {
    if (ob_get_length()) {
        ob_end_flush();
    }
}
add_action('init', 'start_http_to_https_buffer');
add_action('shutdown', 'end_http_to_https_buffer');<br />
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