My PHP Query Function Doesn't Work With INSERT Queries

Question

I created the MySQLi query function below, and it works great with SELECT queries and does everything dynamically so it can work with result sets of any size, but when I try INSERT INTO, I get the message Fatal error: Call to a member function fetch_field() on boolean. I want it to return TRUE or FALSE for queries like INSERT INTO, UPDATE, etc. based on if the query was successful or not. Any suggestions?

Here's the full query function:

    /**
     * Querying the database
     *
     * @param string $query_string The query string to be executed
     * @param array $params The parameters for the query if it is a prepared statement
     *
     * @return mixed The results of the query, either in an array or NULL, or FALSE if executing the query failed
     */
    final public function query($query_string, $params = array()) {

        // Resetting error and result data
        $this->error = FALSE;
        $this->result = array();
        $this->result_metadata = array();

        // Initiating the query statement
        $this->stmt = $this->DB->stmt_init();

        // Preparing the query statement and binding parameters if provided
        if ($this->stmt->prepare($query_string) and count($params)) {

            // Setting the types of each parameter in $params
            $param_types = "";
            foreach ($params as $param) {
                if (is_int($param)) {
                    $param_types .= "i"; continue;
                }
                if (is_float($param)) {
                    $param_types .= "d"; continue;
                }
                if (is_string($param)) {
                    $param_types .= "s"; continue;
                }
                else {
                    $param_types .= "b";
                }
            }

            // Appending the parameter types to the beginning of $params for use in call_user_func_array
            array_unshift($params, $param_types);

            // Creating a reference array and passing all values from $params into it by reference
            $reference = array();
            foreach ($params as $key => $param) {
                $reference[$key] = &$params[$key];
            }

            // Binding the parameters to the query statement
            call_user_func_array(array($this->stmt, "bind_param"), $reference);
        }

        // Executing the query statement
        if (@$this->stmt->execute()) {

            // Fetching the metadata of the result
            $this->result_metadata = $this->stmt->result_metadata();

            // Populating $fields with variables whose name is the value of $field_name indexed under $field_name
            while ($field = $this->result_metadata->fetch_field()) {
                $field_name = $field->name;
                $$field_name = NULL;
                $fields[$field_name] = &$$field_name;
            }

            // Binding the results of the query to $fields
            call_user_func_array(array($this->stmt, "bind_result"), $fields);

            // Storing the results of the query
            $this->stmt->store_result();

            // Fetching the results of the query and storing them in $result_array
            $row = 0;
            while ($this->stmt->fetch()) {
                $result_array[$row] = array();
                foreach ($fields as $key => $field) {
                    $result_array[$row][$key] = $field;
                }
                $row++;
            }

            // Storing the number of rows to self::$num_rows
            $this->num_rows = $this->stmt->num_rows;                

            // Closing the query statement
            $this->stmt->free_result();
            $this->stmt->close();

            // Returning $result_array, or the only element of $result_array if $result_array is of size 1
            return @((count($result_array) === 1) ? $result_array[0] : $result_array);
        }

        // Setting $this->error equal to the DB error and returning FALSE
        else {
            $this->error = $this->DB->error;
            return FALSE;
        }

    }

Community · Accepted Answer · 2017-05-23 12:06:27Z

1

According to the docs, the result_metadata function will only return an object if the query returns a result set. Since an INSERT query only reports success/failure, result_metadata only returns false. See this answer for more details.

But since it only returns FALSE, you can't call fetch_field on it, of course.

edited May 23, 2017 at 12:06

CommunityBot

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answered Apr 8, 2015 at 2:22

xathien

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1 Comment

Alec Over a year ago

Perfect, thanks! I modified the code to detect if $this->result_metadata is FALSE and return if it is. Works flawlessly now.

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