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php – WordPress database insert() and update() – using NULL values

Posted by: admin July 12, 2020 Leave a comment

Questions:

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?

How to&Answers:

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:

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:

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:

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:

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.