メモ用です。

公式ドキュメント

post_exists( string $title, string $content = '', string $date = '', string $type = '' )

index.php


function post_exists( $title, $content = '', $date = '', $type = '' ) {
    global $wpdb;
 
    $post_title   = wp_unslash( sanitize_post_field( 'post_title', $title, 0, 'db' ) );
    $post_content = wp_unslash( sanitize_post_field( 'post_content', $content, 0, 'db' ) );
    $post_date    = wp_unslash( sanitize_post_field( 'post_date', $date, 0, 'db' ) );
    $post_type    = wp_unslash( sanitize_post_field( 'post_type', $type, 0, 'db' ) );
 
    $query = "SELECT ID FROM $wpdb->posts WHERE 1=1";
    $args  = array();
 
    if ( ! empty( $date ) ) {
        $query .= ' AND post_date = %s';
        $args[] = $post_date;
    }
 
    if ( ! empty( $title ) ) {
        $query .= ' AND post_title = %s';
        $args[] = $post_title;
    }
 
    if ( ! empty( $content ) ) {
        $query .= ' AND post_content = %s';
        $args[] = $post_content;
    }
 
    if ( ! empty( $type ) ) {
        $query .= ' AND post_type = %s';
        $args[] = $post_type;
    }
 
    if ( ! empty( $args ) ) {
        return (int) $wpdb->get_var( $wpdb->prepare( $query, $args ) );
    }
 
    return 0;
}