Wordpress 附带处理 CRUD 操作的 wpdb 类。我感兴趣的这个类的两个方法是insert()（CRUD 中的 C）和update()（CRUD 中的 U）。
当我想在 mysql 数据库列中插入 NULL 时出现问题 - wpdb 类将 PHP 空变量转义为空字符串。如何告诉 Wordpress 使用实际的 MySQL NULL 而不是 MySQL 字符串？
【问题讨论】：
标签： php mysql wordpress null crud
wpdb insert() 和 update() 与 NULL 值一起使用，它在多年前就已修补，但从未在 Codex 中提及。
在你的情况下：
$wpdb->update(
'table',
array(
'status' => null,
),
array( 'id' => 1 ),
null,
'%d'
);
【讨论】：
我在Wordpress StackExchange 论坛上找到了这个，对我来说效果很好。
// 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' );
而函数 wp_db_null_value 是：
/**
* Replace the 'NULL' string with NULL
*
* @param string $query
* @return string $query
*/
function wp_db_null_value( $query )
{
return str_ireplace( "'NULL'", "NULL", $query );
}
因为在我的情况下我不能使用 $db->prepare() 函数...
【讨论】：
我尝试编辑此处列出的其他解决方案之一，因为它导致格式数组与数据数组未对齐，但失败了。
这是一个从最新版本的 wordpress 修改 wpdb 的解决方案，以便允许使用 insert() 和 update() 将空值插入和更新到 SQL 表中：
/*
* Fix wpdb to allow inserting/updating of null values into tables
*/
class wpdbfixed extends wpdb
{
function insert($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;
$wpdb_allow_null = new wpdbfixed(DB_USER, DB_PASSWORD, DB_NAME, DB_HOST);
将此代码插入到始终可以运行的位置，例如您的functions.php，然后照常使用新的全局$wpdb_allowed_null->insert() 和->update()。
我更喜欢这种方法而不是覆盖默认的 $wpdb，以便保留其他 Wordpress 和其他插件所期望的 DB 行为。
【讨论】：
这是您的问题的解决方案。在“wp-content”文件夹中，创建一个名为“db.php”的文件并将这段代码放入其中：
<?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))) );
}
}
$wpdb = new wpdbfixed(DB_USER, DB_PASSWORD, DB_NAME, DB_HOST);
?>
通过这种方式，您可以将 null 值 与 wpdb 一起使用！
【讨论】：
如果您希望它兼容，您必须显示列并提前确定是否允许 NULL。如果允许，则如果值为空（$v），则在查询中使用 val = NULL。
$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 ) );
}
【讨论】：