您不必合并数组来在循环中使用它们。您只需要一个可以用作哈希查找的类似密钥。那就是wp_list_pluck 很方便。

// Image Data
$instagrams = array (
    array (
        \'post_id\' => 1,
        \'image\' => \'http://placekitten.com/200/300\',
    ), array (
        \'post_id\' => 2,
        \'image\' => \'http://placekitten.com/200/300\',
    ), array (
        \'post_id\' => 3,
        \'image\' => \'http://placekitten.com/200/300\',
    ),
);

// Transform the array where post_id is the key
$hash = wp_list_pluck( $instagrams, \'image\', \'post_id\' );

// WP_Query arguments
$args = array (
    \'post_type\' => array ( \'post\' ),
    \'post_status\' => array ( \'publish\' ),
    \'posts_per_page\' => \'3\',
);

// The Query
$query = new WP_Query( $args );

// The Loop
if ( $query->have_posts() ) {
    while( $query->have_posts() ) {
        $query->the_post();

        // the ID from the post
        $post_id = get_the_ID();

        // becomes the key to the image array
        if ( isset( $hash[ $post_id ] ) ) {

            $image = $hash[ $post_id ];

            echo $image;
        }
    }
}

wp_reset_postdata();