我有一个自定义插件，可以创建一个管理设置页面，包含3个字段：

帖子、页面ID和消息。

我试图抓取首页列表上显示的第一篇帖子，并将“消息”字段的内容添加到内容的开头。我是在一个插件中完成这项工作的，我不知道如何连接到主页帖子列表，在那里获取第一篇帖子，并在内容之前添加“消息”，然后将其返回。

我想这与pre\\u get\\u posts挂钩有关，但我就是想不出正确的方法。

以下是插件的完整PHP，一切正常，我现在无法找到获取第一篇帖子内容的正确方法：(

<?php
/*
Plugin Name: Custom HTML
Description: Custom HTML in Pages
Version: 1.0.0
*/
class Codeable_Fields_Plugin {
  public function __construct() {
    // Hook into the admin menu
    add_action( \'admin_menu\', array( $this, \'create_plugin_settings_page\' ) );
    // Add Settings and Fields
    add_action( \'admin_init\', array( $this, \'setup_sections\' ) );
    add_action( \'admin_init\', array( $this, \'setup_fields\' ) );
  }
  public function create_plugin_settings_page() {
    // Add the menu item and page
    $page_title = \'Custom HTML\';
    $menu_title = \'Custom HTML\';
    $capability = \'manage_options\';
    $slug = \'codeable_fields\';
    $callback = array( $this, \'plugin_settings_page_content\' );
    $position = 100;
    add_menu_page( $page_title, $menu_title, $capability, $slug, $callback, $icon, $position );
  }
  public function plugin_settings_page_content() {?>
    <div class="wrap">
      <?php
      if ( isset( $_GET[\'settings-updated\'] ) && $_GET[\'settings-updated\'] ){
        $this->admin_notice();
      } ?>
      <form method="POST" action="options.php">
      <?php
        settings_fields( \'codeable_fields\' );
        do_settings_sections( \'codeable_fields\' );
        submit_button();
      ?>
      </form>
    </div> <?php
  }
  public function admin_notice() { ?>
    <div class="notice notice-success is-dismissible">
      <p>Your settings have been updated!</p>
    </div><?php
  }
  public function setup_sections() {
    add_settings_section( \'our_first_section\', \'Custom HTML\', array( $this, \'section_callback\' ), \'codeable_fields\' );
  }
  public function section_callback( $arguments ) {
    switch( $arguments[\'id\'] ){
      case \'our_first_section\':
        echo \'\';
        break;
      }
  }
  public function setup_fields() {
    $fields = array(
      array(
        \'uid\' => \'codeable_pages_field\',
        \'label\' => \'Page IDs to Exclude\',
        \'section\' => \'our_first_section\',
        \'type\' => \'text\',
        \'supplimental\' => \'Seperate by comma\',
      ),
      array(
        \'uid\' => \'codeable_posts_field\',
        \'label\' => \'Post IDs to Exclude\',
        \'section\' => \'our_first_section\',
        \'type\' => \'text\',
        \'supplimental\' => \'Seperate by comma\',
      ),
      array(
        \'uid\' => \'codeable_textarea\',
        \'label\' => \'Enter Text here\',
        \'section\' => \'our_first_section\',
        \'type\' => \'textarea\',
      )
    );
    foreach( $fields as $field ){
      add_settings_field( $field[\'uid\'], $field[\'label\'], array( $this, \'field_callback\' ), \'codeable_fields\', $field[\'section\'], $field );
      register_setting( \'codeable_fields\', $field[\'uid\'] );
    }
  }
  public function field_callback( $arguments ) {
    $value = get_option( $arguments[\'uid\'] );
    if( ! $value ) {
      $value = $arguments[\'default\'];
    }
    switch( $arguments[\'type\'] ){
      case \'text\':
      case \'password\':
      case \'number\':
        printf( \'<input name="%1$s" id="%1$s" type="%2$s" placeholder="%3$s" value="%4$s" />\', $arguments[\'uid\'], $arguments[\'type\'], $arguments[\'placeholder\'], $value );
        break;
      case \'textarea\':
        printf( \'<textarea name="%1$s" id="%1$s" placeholder="%2$s" rows="5" cols="50">%3$s</textarea>\', $arguments[\'uid\'], $arguments[\'placeholder\'], $value );
        break;
      case \'select\':
      case \'multiselect\':
        if( ! empty ( $arguments[\'options\'] ) && is_array( $arguments[\'options\'] ) ){
          $attributes = \'\';
          $options_markup = \'\';
          foreach( $arguments[\'options\'] as $key => $label ){
            $options_markup .= sprintf( \'<option value="%s" %s>%s</option>\', $key, selected( $value[ array_search( $key, $value, true ) ], $key, false ), $label );
          }
          if( $arguments[\'type\'] === \'multiselect\' ){
            $attributes = \' multiple="multiple" \';
          }
          printf( \'<select name="%1$s[]" id="%1$s" %2$s>%3$s</select>\', $arguments[\'uid\'], $attributes, $options_markup );
        }
        break;
      case \'radio\':
      case \'checkbox\':
        if( ! empty ( $arguments[\'options\'] ) && is_array( $arguments[\'options\'] ) ){
          $options_markup = \'\';
          $iterator = 0;
          foreach( $arguments[\'options\'] as $key => $label ){
            $iterator++;
            $options_markup .= sprintf( \'<label for="%1$s_%6$s"><input id="%1$s_%6$s" name="%1$s[]" type="%2$s" value="%3$s" %4$s /> %5$s</label><br/>\', $arguments[\'uid\'], $arguments[\'type\'], $key, checked( $value[ array_search( $key, $value, true ) ], $key, false ), $label, $iterator );
          }
          printf( \'<fieldset>%s</fieldset>\', $options_markup );
        }
        break;
      }
      if( $helper = $arguments[\'helper\'] ){
        printf( \'<span class="helper"> %s</span>\', $helper );
      }
      if( $supplimental = $arguments[\'supplimental\'] ){
        printf( \'<p class="description">%s</p>\', $supplimental );
      }
    }
  }
}
new Codeable_Fields_Plugin();

add_action (\'the_content\', \'add_to_header\');
function add_to_header(){
  $postids = preg_split("/\\s*,\\s*/", get_option(\'codeable_posts_field\'));
  $pageids = preg_split("/\\s*,\\s*/", get_option(\'codeable_pages_field\'));

  if (is_single($postids )) {
    $fullcontent = $content;
  }
  elseif (is_page($pageids)) {
    $fullcontent = $content;
  }
  elseif (is_single() || is_page()) {
    $beforecontent = get_option(\'codeable_textarea\');
    $fullcontent = $beforecontent . $content;
  }
  return $fullcontent;
}