Change the vote

Additionally. Instead of changing the vote, I tried to remove it from database using the follow:

if ( function_exists( 'the_field' ) ) {
		global $wpdb;

		$results = $wpdb->get_results( "SELECT rating FROM $wpdb->acfsrf where user_id=".get_current_user_id()." AND meta_id=".get_the_ID() );
		if ($results != NULL){
			 function removeVote() {
					global $wpdb;
					$results2 = $wpdb->delete( $wpdb->acfsrf , array( 'user_id' => get_current_user_id(), 'meta_id' => get_the_ID()  ) );
					if ($results2){
						echo "deleted successfully";
					}
				}

				if (isset($_GET['vote_remove'])) {
					removeVote();
				}
				?>
				<a href='index.php?vote_remove=true'>Remove your rate!</a>
		<?php } else{
	        $star_rating = get_field( 'field_55b60d9089739', get_the_ID());
	        print_r($star_rating);
    	}
    }

I managed to remove the row from database. And the user can vote again. However the data persist. May I know where else do I have to remove aside from wp_acfsrf?

Thank you.

Thanks for hint.

I am not sure if I did it correctly but I managed to get it working.

if ( function_exists( 'the_field' ) ) {
		global $wpdb;

		$result = $wpdb->get_results( "SELECT rating FROM $wpdb->acfsrf where user_id=".get_current_user_id()." AND meta_id=".get_the_ID() );
		if ($result != NULL){
			 function removeVote() {
					global $wpdb;
					//GET current user rating
					$result2 = $wpdb->get_results( "SELECT rating FROM $wpdb->acfsrf where user_id=".get_current_user_id()." AND meta_id=".get_the_ID() );
					$current_rate = ($result2[0]->rating);

					//GET the current result and segregate result
					$result3 = $wpdb->get_results( "SELECT meta_value FROM $wpdb->postmeta where meta_key='rate' AND post_id=".get_the_ID() );
					$ratearray = explode(";", $result3[0]->meta_value);

					//Remove d: and i: from string
					$total_rate = str_replace("d:", "", $ratearray[1]);
					$total_user = str_replace("i:", "", $ratearray[3]);

					//Update the respective value
					$updated_user = $total_user-1;
					$updated_rate = (($total_rate * $total_user)-$current_rate)/($updated_user);

					//convert value to string
					$new_value = "$ratearray[0];d:$updated_rate;$ratearray[2];i:$updated_user;$ratearray[4]";

					//Update table with user
					$result4 = $wpdb->update($wpdb->postmeta , array('meta_value' => $new_value), array('meta_key' => 'rate', 'post_id' => get_the_ID()));

					//remove the current user rate
					$result5 = $wpdb->delete( $wpdb->acfsrf , array( 'user_id' => get_current_user_id(), 'meta_id' => get_the_ID()  ) );
					if ($result5 && $result4){
						wp_redirect( add_query_arg( array('vote_remove' => false), $_SERVER['REQUEST_URI']) );
						exit;
					}
				}

				if (isset($_GET['vote_remove'])) {
					removeVote();
				}
				?>
				<a href='index.php?vote_remove=true'>Remove your rate!</a>
		<?php } else{
	        $star_rating = get_field( 'field_55b60d9089739', get_the_ID());
	        print_r($star_rating);
    	}
    }

So you actually serialize the code before inserting to DB.

Thanks for the tips that actually helped me optimized my code.