Wordpress database insert() and update() - using NULL values

Question

Wordpress ships with the wpdb class which handles CRUD operations. The two methods of this class that I'm interested in are the insert() (the C in CRUD) and update() (the U in CRUD).

A problem arises when I want to insert a NULL into a mysql database column - the wpdb class escapes PHP null variables to empty strings. How can I tell Wordpress to use an actual MySQL NULL instead of a MySQL string?

Answer 1

Here's a solution to your problem. In "wp-content" folder, create a file named "db.php" and put this code in it:

<?php

// setup a dummy wpdb to prevent the default one from being instanciated
$wpdb = new stdclass();

// include the base wpdb class to inherit from
//include ABSPATH . WPINC . "/wp-db.php";


class wpdbfixed extends wpdb
{
    function insert($table, $data, $format = null) {
        $formats = $format = (array) $format;
        $fields = array_keys($data);
        $formatted_fields = array();
        $real_data = array();
        foreach ( $fields as $field ) {
            if ($data[$field]===null)
            {
                $formatted_fields[] = 'NULL';
                continue;
            }
            if ( !empty($format) )
                $form = ( $form = array_shift($formats) ) ? $form : $format[0];
            elseif ( isset($this->field_types[$field]) )
                $form = $this->field_types[$field];
            else
                $form = '%s';
            $formatted_fields[] = "'".$form."'";
            $real_data[] = $data[$field];
        }
        //$sql = "INSERT INTO <code>$table</code> (<code>&quot; . implode( '</code>,<code>', $fields ) . &quot;</code>) VALUES (" . implode( ",", $formatted_fields ) . ")";
        $sql = "INSERT INTO $table (" . implode( ',', $fields ) . ") VALUES (" . implode( ",", $formatted_fields ) . ")";
        return $this->query( $this->prepare( $sql, $real_data) );
    }

    function update($table, $data, $where, $format = null, $where_format = null)
    {
        if ( !is_array( $where ) )
            return false;

        $formats = $format = (array) $format;
        $bits = $wheres = array();
        $fields = (array) array_keys($data);
        $real_data = array();
        foreach ( $fields as $field ) {
            if ($data[$field]===null)
            {
                $bits[] = "$field = NULL";
                continue;
            }
            if ( !empty($format) )
                $form = ( $form = array_shift($formats) ) ? $form : $format[0];
            elseif ( isset($this->field_types[$field]) )
                $form = $this->field_types[$field];
            else
                $form = '%s';
            $bits[] = "$field = {$form}";

            $real_data[] = $data[$field];
        }

        $where_formats = $where_format = (array) $where_format;
        $fields = (array) array_keys($where);
        foreach ( $fields as $field ) {
            if ( !empty($where_format) )
                $form = ( $form = array_shift($where_formats) ) ? $form : $where_format[0];
            elseif ( isset($this->field_types[$field]) )
                $form = $this->field_types[$field];
            else
                $form = '%s';
            $wheres[] = "$field = {$form}";
        }

        $sql = "UPDATE $table SET " . implode( ', ', $bits ) . ' WHERE ' . implode( ' AND ', $wheres );

        return $this->query( $this->prepare( $sql, array_merge($real_data, array_values($where))) );
    }

}

$wpdb = new wpdbfixed(DB_USER, DB_PASSWORD, DB_NAME, DB_HOST);
?>

In this way you can use null values with wpdb!

Answer 2

If you want it to compatible you would have to SHOW COLUMN and determine ahead if NULL is allowed. If it was allowed then if the value was empty($v) use val = NULL in the query.

$foo = null;
$metakey = "Harriet's Adages";
$metavalue = "WordPress' database interface is like Sunday Morning: Easy.";

if ($foo == null) {
$wpdb->query( $wpdb->prepare( "
    INSERT INTO $wpdb->postmeta
    ( post_id, meta_key, meta_value, field_with_null )
    VALUES ( %d, %s, %s, NULL )", 
        10, $metakey, $metavalue ) );
} else {
$wpdb->query( $wpdb->prepare( "
    INSERT INTO $wpdb->postmeta
    ( post_id, meta_key, meta_value, field_with_null )
    VALUES ( %d, %s, %s, %s)", 
        10, $metakey, $metavalue, $foo ) );
}

Answer 3

I find this on Wordpress StackExchange forum and it works very well for me.

// Add a filter to replace the 'NULL' string with NULL
add_filter( 'query', 'wp_db_null_value' );

global $wpdb;
$wpdb->update(
    'table',
    array( 
        'status' => 'NULL',
    ), 
    array( 'id' => 1 ) 
);

// Remove the filter again:
remove_filter( 'query', 'wp_db_null_value' );

and the function wp_db_null_value is:

/**
* Replace the 'NULL' string with NULL
* 
* @param  string $query
* @return string $query
*/

function wp_db_null_value( $query )
{
  return str_ireplace( "'NULL'", "NULL", $query ); 
}

Because in my case I cannot use $db->prepare() function...