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

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

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 2

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>" . implode( '</code>,<code>', $fields ) . "</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 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...

Answer 4

wpdb insert() and update() works with NULL values, it was patched many years ago but never mentioned in the Codex.
In your case:
$wpdb->update(
'table',
array(
'status' => null,
),
array( 'id' => 1 ),
null,
'%d'
);
Ref: https://core.trac.wordpress.org/ticket/15158#no0

Answer 5

I tried to edit one of the other solutions listed here, because it resulted in the format array being misaligned with the data array, but failed.
Here is a solution that modifies the wpdb from the latest version of wordpress, in order to allow inserting and updating null values into SQL tables using insert() and update():
/*
* Fix wpdb to allow inserting/updating of null values into tables
*/
class wpdbfixed extends wpdb
{
function insert($table, $data, $format = null) {
$type = 'INSERT';
if ( ! in_array( strtoupper( $type ), array( 'REPLACE', 'INSERT' ) ) )
return false;
$this->insert_id = 0;
$formats = $format = (array) $format;
$fields = array_keys( $data );
$formatted_fields = array();
foreach ( $fields as $field ) {
if ( !empty( $format ) )
$form = ( $form = array_shift( $formats ) ) ? $form : $format[0];
elseif ( isset( $this->field_types[$field] ) )
$form = $this->field_types[$field];
else
$form = '%s';
//***Steve Lee edit begin here***
if ($data[$field]===null) {
unset($data[$field]); //Remove this element from array, so we don't try to insert its value into the %s/%d/%f parts during prepare(). Without this, array would become shifted.
$formatted_fields[] = 'NULL';
} else {
$formatted_fields[] = $form; //Original line of code
}
//***Steve Lee edit ends here***
}
$sql = "{$type} INTO `$table` (`" . implode( '`,`', $fields ) . "`) VALUES (" . implode( ",", $formatted_fields ) . ")";
return $this->query( $this->prepare( $sql, $data ) );
}
function update($table, $data, $where, $format = null, $where_format = null)
{
if ( ! is_array( $data ) || ! is_array( $where ) )
return false;
$formats = $format = (array) $format;
$bits = $wheres = array();
foreach ( (array) array_keys( $data ) as $field ) {
if ( !empty( $format ) )
$form = ( $form = array_shift( $formats ) ) ? $form : $format[0];
elseif ( isset($this->field_types[$field]) )
$form = $this->field_types[$field];
else
$form = '%s';
//***Steve Lee edit begin here***
if ($data[$field]===null)
{
unset($data[$field]); //Remove this element from array, so we don't try to insert its value into the %s/%d/%f parts during prepare(). Without this, array would become shifted.
$bits[] = "`$field` = NULL";
} else {
$bits[] = "`$field` = {$form}"; //Original line of code
}
//***Steve Lee edit ends here***
}
$where_formats = $where_format = (array) $where_format;
foreach ( (array) array_keys( $where ) 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( array_values( $data ), array_values( $where ) ) ) );
}
}
global $wpdb_allow_null;
$wpdb_allow_null = new wpdbfixed(DB_USER, DB_PASSWORD, DB_NAME, DB_HOST);
Insert this code into somewhere that always gets run, like your functions.php, and then use your new global $wpdb_allowed_null->insert() and ->update() as normal.
I preferred this method vs. overriding the default $wpdb, in order to preserve the DB behavior that the rest of Wordpress and other plugins will expect.