【WordPress】対処法:1件の致命的な問題 バックグラウンド更新が想定通りに動作していません。wp-admin/install.phpから書き込みできません。

big-caution-mark-on-laptop-working-people-around.jpgWordPress

WordPressのヘルスチェックで、以下のような致命的なエラーが発生したときの対処法について。

エラー内容

1件の致命的な問題

バックグラウンド更新が想定通りに動作していません

セキュリティ

✓ バックグラウンド更新は使用中の WordPress のバージョンにセキュリティ更新がリリースされた際、自動更新できることを保証します。

✓ OK バージョン管理システムは検出されませんでした。

✓ OK この WordPress サイトでは更新の実行の際に FTP 認証情報を必要としません。

× エラー 一部のファイルが WordPress から書き込みできません: wp-admin/install.php

エラーの原因

サイトのディレクトリ配下の、wp-admin > install.php ファイルにアクセス権限が付与されていない。

サイトの権限を確認すると、すべてのユーザーに対して、読み込み、書き込み、実行のすべての権限が無しになっている。

このファイルはWordpressの初期インストールや再度初期化するためのもの。指定のURLを入力すればアクセスできてしまう。

初期化の実行にはログインが必要なので、基本的には安全性は守られている。

対処法

対処法は大きく2つ。

  1. ファイルを削除する。
  2. オーナーにアクセス権限を付与し、リダイレクト設定をする。

ファイルを削除する

このファイルは初期インストールが完了したら不要になるので、削除してしまっても問題ない。

なお、ファイルを削除するときは「/wp-admin/install-helper.php」も合わせて削除する。こちらもインストール時のみに使うファイルで、消してしまっても問題ない。

ファイルを削除して、管理画面でサイトヘルスをリロードすれば、致命的な問題が改善され、サイトヘルスが良好になる。

オーナーにアクセス権限を付与し、リダイレクト設定をする。

再インストールの可能性がある場合は、オーナーに、読み込み、書き込み、実行権限を付与し、リダイレクト設定をかけておくことも可能。

FTPソフトで該当のファイルにアクセスし、権限を 700 に変更する。

例えば、lolipopサーバーの場合は、右上の「現在の属性」に700を入力し、「保存する」をクリックすると、権限が変更されファイルの内容が閲覧できるようになる。

次に、 .htaccess 開いて、以下のリダイレクト設定を追記する。


#install.phpのリダイレクト
RedirectMatch Permanent wp-admin/install(-helper)?\.php /


管理画面でサイトヘルスをリロードすれば、致命的な問題が改善され、サイトヘルスが良好になる。

wp-admin/install.phpファイルとは?

そもそも、今回エラーの原因となったwp-admin/install.phpファイルは、Wordpressの初期インストール時に必要なファイルになる。

ちなみに、ドメインの後ろに wp-admin/install.php とつけてアクセスすれば、以下のように再インストールの確認画面が表示されるので、すぐに初期化されたり、誰でも初期化できるということはない。

ファイルを削除したあとに再度必要になった場合は以下ご参考。

wp-admin/install.phpのコード

<?php
/**
 * WordPress Installer
 *
 * @package WordPress
 * @subpackage Administration
 */

// Sanity check.
if ( false ) {
	?>
<!DOCTYPE html>
<html>
<head>
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
	<title>Error: PHP is not running</title>
</head>
<body class="wp-core-ui">
	<p id="logo"><a href="https://wordpress.org/">WordPress</a></p>
	<h1>Error: PHP is not running</h1>
	<p>WordPress requires that your web server is running PHP. Your server does not have PHP installed, or PHP is turned off.</p>
</body>
</html>
	<?php
}

/**
 * We are installing WordPress.
 *
 * @since 1.5.1
 * @var bool
 */
define( 'WP_INSTALLING', true );

/** Load WordPress Bootstrap */
require_once dirname( __DIR__ ) . '/wp-load.php';

/** Load WordPress Administration Upgrade API */
require_once ABSPATH . 'wp-admin/includes/upgrade.php';

/** Load WordPress Translation Install API */
require_once ABSPATH . 'wp-admin/includes/translation-install.php';

/** Load wpdb */
require_once ABSPATH . WPINC . '/wp-db.php';

nocache_headers();

$step = isset( $_GET['step'] ) ? (int) $_GET['step'] : 0;

/**
 * Display installation header.
 *
 * @since 2.5.0
 *
 * @param string $body_classes
 */
function display_header( $body_classes = '' ) {
	header( 'Content-Type: text/html; charset=utf-8' );
	if ( is_rtl() ) {
		$body_classes .= 'rtl';
	}
	if ( $body_classes ) {
		$body_classes = ' ' . $body_classes;
	}
	?>
<!DOCTYPE html>
<html <?php language_attributes(); ?>>
<head>
	<meta name="viewport" content="width=device-width" />
	<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
	<meta name="robots" content="noindex,nofollow" />
	<title><?php _e( 'WordPress › Installation' ); ?></title>
	<?php wp_admin_css( 'install', true ); ?>
</head>
<body class="wp-core-ui<?php echo $body_classes; ?>">
<p id="logo"><?php _e( 'WordPress' ); ?></p>

	<?php
} // End display_header().

/**
 * Display installer setup form.
 *
 * @since 2.8.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param string|null $error
 */
function display_setup_form( $error = null ) {
	global $wpdb;

	$user_table = ( $wpdb->get_var( $wpdb->prepare( 'SHOW TABLES LIKE %s', $wpdb->esc_like( $wpdb->users ) ) ) !== null );

	// Ensure that sites appear in search engines by default.
	$blog_public = 1;
	if ( isset( $_POST['weblog_title'] ) ) {
		$blog_public = isset( $_POST['blog_public'] );
	}

	$weblog_title = isset( $_POST['weblog_title'] ) ? trim( wp_unslash( $_POST['weblog_title'] ) ) : '';
	$user_name    = isset( $_POST['user_name'] ) ? trim( wp_unslash( $_POST['user_name'] ) ) : '';
	$admin_email  = isset( $_POST['admin_email'] ) ? trim( wp_unslash( $_POST['admin_email'] ) ) : '';

	if ( ! is_null( $error ) ) {
		?>
<h1><?php _ex( 'Welcome', 'Howdy' ); ?></h1>
<p class="message"><?php echo $error; ?></p>
<?php } ?>
<form id="setup" method="post" action="install.php?step=2" novalidate="novalidate">
	<table class="form-table" role="presentation">
		<tr>
			<th scope="row"><label for="weblog_title"><?php _e( 'Site Title' ); ?></label></th>
			<td><input name="weblog_title" type="text" id="weblog_title" size="25" value="<?php echo esc_attr( $weblog_title ); ?>" /></td>
		</tr>
		<tr>
			<th scope="row"><label for="user_login"><?php _e( 'Username' ); ?></label></th>
			<td>
			<?php
			if ( $user_table ) {
				_e( 'User(s) already exists.' );
				echo '<input name="user_name" type="hidden" value="admin" />';
			} else {
				?>
				<input name="user_name" type="text" id="user_login" size="25" value="<?php echo esc_attr( sanitize_user( $user_name, true ) ); ?>" />
				<p><?php _e( 'Usernames can have only alphanumeric characters, spaces, underscores, hyphens, periods, and the @ symbol.' ); ?></p>
				<?php
			}
			?>
			</td>
		</tr>
		<?php if ( ! $user_table ) : ?>
		<tr class="form-field form-required user-pass1-wrap">
			<th scope="row">
				<label for="pass1">
					<?php _e( 'Password' ); ?>
				</label>
			</th>
			<td>
				<div class="wp-pwd">
					<?php $initial_password = isset( $_POST['admin_password'] ) ? stripslashes( $_POST['admin_password'] ) : wp_generate_password( 18 ); ?>
					<input type="password" name="admin_password" id="pass1" class="regular-text" autocomplete="off" data-reveal="1" data-pw="<?php echo esc_attr( $initial_password ); ?>" aria-describedby="pass-strength-result" />
					<button type="button" class="button wp-hide-pw hide-if-no-js" data-start-masked="<?php echo (int) isset( $_POST['admin_password'] ); ?>" data-toggle="0" aria-label="<?php esc_attr_e( 'Hide password' ); ?>">
						<span class="dashicons dashicons-hidden"></span>
						<span class="text"><?php _e( 'Hide' ); ?></span>
					</button>
					<div id="pass-strength-result" aria-live="polite"></div>
				</div>
				<p><span class="description important hide-if-no-js">
				<strong><?php _e( 'Important:' ); ?></strong>
				<?php /* translators: The non-breaking space prevents 1Password from thinking the text "log in" should trigger a password save prompt. */ ?>
				<?php _e( 'You will need this password to log in. Please store it in a secure location.' ); ?></span></p>
			</td>
		</tr>
		<tr class="form-field form-required user-pass2-wrap hide-if-js">
			<th scope="row">
				<label for="pass2"><?php _e( 'Repeat Password' ); ?>
					<span class="description"><?php _e( '(required)' ); ?></span>
				</label>
			</th>
			<td>
				<input name="admin_password2" type="password" id="pass2" autocomplete="off" />
			</td>
		</tr>
		<tr class="pw-weak">
			<th scope="row"><?php _e( 'Confirm Password' ); ?></th>
			<td>
				<label>
					<input type="checkbox" name="pw_weak" class="pw-checkbox" />
					<?php _e( 'Confirm use of weak password' ); ?>
				</label>
			</td>
		</tr>
		<?php endif; ?>
		<tr>
			<th scope="row"><label for="admin_email"><?php _e( 'Your Email' ); ?></label></th>
			<td><input name="admin_email" type="email" id="admin_email" size="25" value="<?php echo esc_attr( $admin_email ); ?>" />
			<p><?php _e( 'Double-check your email address before continuing.' ); ?></p></td>
		</tr>
		<tr>
			<th scope="row"><?php has_action( 'blog_privacy_selector' ) ? _e( 'Site visibility' ) : _e( 'Search engine visibility' ); ?></th>
			<td>
				<fieldset>
					<legend class="screen-reader-text"><span><?php has_action( 'blog_privacy_selector' ) ? _e( 'Site visibility' ) : _e( 'Search engine visibility' ); ?> </span></legend>
					<?php
					if ( has_action( 'blog_privacy_selector' ) ) {
						?>
						<input id="blog-public" type="radio" name="blog_public" value="1" <?php checked( 1, $blog_public ); ?> />
						<label for="blog-public"><?php _e( 'Allow search engines to index this site' ); ?></label><br/>
						<input id="blog-norobots" type="radio" name="blog_public" value="0" <?php checked( 0, $blog_public ); ?> />
						<label for="blog-norobots"><?php _e( 'Discourage search engines from indexing this site' ); ?></label>
						<p class="description"><?php _e( 'Note: Neither of these options blocks access to your site — it is up to search engines to honor your request.' ); ?></p>
						<?php
						/** This action is documented in wp-admin/options-reading.php */
						do_action( 'blog_privacy_selector' );
					} else {
						?>
						<label for="blog_public"><input name="blog_public" type="checkbox" id="blog_public" value="0" <?php checked( 0, $blog_public ); ?> />
						<?php _e( 'Discourage search engines from indexing this site' ); ?></label>
						<p class="description"><?php _e( 'It is up to search engines to honor this request.' ); ?></p>
					<?php } ?>
				</fieldset>
			</td>
		</tr>
	</table>
	<p class="step"><?php submit_button( __( 'Install WordPress' ), 'large', 'Submit', false, array( 'id' => 'submit' ) ); ?></p>
	<input type="hidden" name="language" value="<?php echo isset( $_REQUEST['language'] ) ? esc_attr( $_REQUEST['language'] ) : ''; ?>" />
</form>
	<?php
} // End display_setup_form().

// Let's check to make sure WP isn't already installed.
if ( is_blog_installed() ) {
	display_header();
	die(
		'<h1>' . __( 'Already Installed' ) . '</h1>' .
		'<p>' . __( 'You appear to have already installed WordPress. To reinstall please clear your old database tables first.' ) . '</p>' .
		'<p class="step"><a href="' . esc_url( wp_login_url() ) . '" class="button button-large">' . __( 'Log In' ) . '</a></p>' .
		'</body></html>'
	);
}

/**
 * @global string $wp_version             The WordPress version string.
 * @global string $required_php_version   The required PHP version string.
 * @global string $required_mysql_version The required MySQL version string.
 */
global $wp_version, $required_php_version, $required_mysql_version;

$php_version   = phpversion();
$mysql_version = $wpdb->db_version();
$php_compat    = version_compare( $php_version, $required_php_version, '>=' );
$mysql_compat  = version_compare( $mysql_version, $required_mysql_version, '>=' ) || file_exists( WP_CONTENT_DIR . '/db.php' );

$version_url = sprintf(
	/* translators: %s: WordPress version. */
	esc_url( __( 'https://wordpress.org/support/wordpress-version/version-%s/' ) ),
	sanitize_title( $wp_version )
);

$php_update_message = '</p><p>' . sprintf(
	/* translators: %s: URL to Update PHP page. */
	__( '<a href="%s">Learn more about updating PHP</a>.' ),
	esc_url( wp_get_update_php_url() )
);

$annotation = wp_get_update_php_annotation();

if ( $annotation ) {
	$php_update_message .= '</p><p><em>' . $annotation . '</em>';
}

if ( ! $mysql_compat && ! $php_compat ) {
	$compat = sprintf(
		/* translators: 1: URL to WordPress release notes, 2: WordPress version number, 3: Minimum required PHP version number, 4: Minimum required MySQL version number, 5: Current PHP version number, 6: Current MySQL version number. */
		__( 'You cannot install because <a href="%1$s">WordPress %2$s</a> requires PHP version %3$s or higher and MySQL version %4$s or higher. You are running PHP version %5$s and MySQL version %6$s.' ),
		$version_url,
		$wp_version,
		$required_php_version,
		$required_mysql_version,
		$php_version,
		$mysql_version
	) . $php_update_message;
} elseif ( ! $php_compat ) {
	$compat = sprintf(
		/* translators: 1: URL to WordPress release notes, 2: WordPress version number, 3: Minimum required PHP version number, 4: Current PHP version number. */
		__( 'You cannot install because <a href="%1$s">WordPress %2$s</a> requires PHP version %3$s or higher. You are running version %4$s.' ),
		$version_url,
		$wp_version,
		$required_php_version,
		$php_version
	) . $php_update_message;
} elseif ( ! $mysql_compat ) {
	$compat = sprintf(
		/* translators: 1: URL to WordPress release notes, 2: WordPress version number, 3: Minimum required MySQL version number, 4: Current MySQL version number. */
		__( 'You cannot install because <a href="%1$s">WordPress %2$s</a> requires MySQL version %3$s or higher. You are running version %4$s.' ),
		$version_url,
		$wp_version,
		$required_mysql_version,
		$mysql_version
	);
}

if ( ! $mysql_compat || ! $php_compat ) {
	display_header();
	die( '<h1>' . __( 'Requirements Not Met' ) . '</h1><p>' . $compat . '</p></body></html>' );
}

if ( ! is_string( $wpdb->base_prefix ) || '' === $wpdb->base_prefix ) {
	display_header();
	die(
		'<h1>' . __( 'Configuration Error' ) . '</h1>' .
		'<p>' . sprintf(
			/* translators: %s: wp-config.php */
			__( 'Your %s file has an empty database table prefix, which is not supported.' ),
			'<code>wp-config.php</code>'
		) . '</p></body></html>'
	);
}

// Set error message if DO_NOT_UPGRADE_GLOBAL_TABLES isn't set as it will break install.
if ( defined( 'DO_NOT_UPGRADE_GLOBAL_TABLES' ) ) {
	display_header();
	die(
		'<h1>' . __( 'Configuration Error' ) . '</h1>' .
		'<p>' . sprintf(
			/* translators: %s: DO_NOT_UPGRADE_GLOBAL_TABLES */
			__( 'The constant %s cannot be defined when installing WordPress.' ),
			'<code>DO_NOT_UPGRADE_GLOBAL_TABLES</code>'
		) . '</p></body></html>'
	);
}

/**
 * @global string    $wp_local_package Locale code of the package.
 * @global WP_Locale $wp_locale        WordPress date and time locale object.
 */
$language = '';
if ( ! empty( $_REQUEST['language'] ) ) {
	$language = preg_replace( '/[^a-zA-Z0-9_]/', '', $_REQUEST['language'] );
} elseif ( isset( $GLOBALS['wp_local_package'] ) ) {
	$language = $GLOBALS['wp_local_package'];
}

$scripts_to_print = array( 'jquery' );

switch ( $step ) {
	case 0: // Step 0.
		if ( wp_can_install_language_pack() && empty( $language ) ) {
			$languages = wp_get_available_translations();
			if ( $languages ) {
				$scripts_to_print[] = 'language-chooser';
				display_header( 'language-chooser' );
				echo '<form id="setup" method="post" action="?step=1">';
				wp_install_language_form( $languages );
				echo '</form>';
				break;
			}
		}

		// Deliberately fall through if we can't reach the translations API.

	case 1: // Step 1, direct link or from language chooser.
		if ( ! empty( $language ) ) {
			$loaded_language = wp_download_language_pack( $language );
			if ( $loaded_language ) {
				load_default_textdomain( $loaded_language );
				$GLOBALS['wp_locale'] = new WP_Locale();
			}
		}

		$scripts_to_print[] = 'user-profile';

		display_header();
		?>
<h1><?php _ex( 'Welcome', 'Howdy' ); ?></h1>
<p><?php _e( 'Welcome to the famous five-minute WordPress installation process! Just fill in the information below and you’ll be on your way to using the most extendable and powerful personal publishing platform in the world.' ); ?></p>

<h2><?php _e( 'Information needed' ); ?></h2>
<p><?php _e( 'Please provide the following information. Don’t worry, you can always change these settings later.' ); ?></p>

		<?php
		display_setup_form();
		break;
	case 2:
		if ( ! empty( $language ) && load_default_textdomain( $language ) ) {
			$loaded_language      = $language;
			$GLOBALS['wp_locale'] = new WP_Locale();
		} else {
			$loaded_language = 'en_US';
		}

		if ( ! empty( $wpdb->error ) ) {
			wp_die( $wpdb->error->get_error_message() );
		}

		$scripts_to_print[] = 'user-profile';

		display_header();
		// Fill in the data we gathered.
		$weblog_title         = isset( $_POST['weblog_title'] ) ? trim( wp_unslash( $_POST['weblog_title'] ) ) : '';
		$user_name            = isset( $_POST['user_name'] ) ? trim( wp_unslash( $_POST['user_name'] ) ) : '';
		$admin_password       = isset( $_POST['admin_password'] ) ? wp_unslash( $_POST['admin_password'] ) : '';
		$admin_password_check = isset( $_POST['admin_password2'] ) ? wp_unslash( $_POST['admin_password2'] ) : '';
		$admin_email          = isset( $_POST['admin_email'] ) ? trim( wp_unslash( $_POST['admin_email'] ) ) : '';
		$public               = isset( $_POST['blog_public'] ) ? (int) $_POST['blog_public'] : 1;

		// Check email address.
		$error = false;
		if ( empty( $user_name ) ) {
			// TODO: Poka-yoke.
			display_setup_form( __( 'Please provide a valid username.' ) );
			$error = true;
		} elseif ( sanitize_user( $user_name, true ) !== $user_name ) {
			display_setup_form( __( 'The username you provided has invalid characters.' ) );
			$error = true;
		} elseif ( $admin_password !== $admin_password_check ) {
			// TODO: Poka-yoke.
			display_setup_form( __( 'Your passwords do not match. Please try again.' ) );
			$error = true;
		} elseif ( empty( $admin_email ) ) {
			// TODO: Poka-yoke.
			display_setup_form( __( 'You must provide an email address.' ) );
			$error = true;
		} elseif ( ! is_email( $admin_email ) ) {
			// TODO: Poka-yoke.
			display_setup_form( __( 'Sorry, that isn’t a valid email address. Email addresses look like <code>username@example.com</code>.' ) );
			$error = true;
		}

		if ( false === $error ) {
			$wpdb->show_errors();
			$result = wp_install( $weblog_title, $user_name, $admin_email, $public, '', wp_slash( $admin_password ), $loaded_language );
			?>

<h1><?php _e( 'Success!' ); ?></h1>

<p><?php _e( 'WordPress has been installed. Thank you, and enjoy!' ); ?></p>

<table class="form-table install-success">
	<tr>
		<th><?php _e( 'Username' ); ?></th>
		<td><?php echo esc_html( sanitize_user( $user_name, true ) ); ?></td>
	</tr>
	<tr>
		<th><?php _e( 'Password' ); ?></th>
		<td>
			<?php if ( ! empty( $result['password'] ) && empty( $admin_password_check ) ) : ?>
				<code><?php echo esc_html( $result['password'] ); ?></code><br />
			<?php endif; ?>
			<p><?php echo $result['password_message']; ?></p>
		</td>
	</tr>
</table>

<p class="step"><a href="<?php echo esc_url( wp_login_url() ); ?>" class="button button-large"><?php _e( 'Log In' ); ?></a></p>

			<?php
		}
		break;
}

if ( ! wp_is_mobile() ) {
	?>
<script type="text/javascript">var t = document.getElementById('weblog_title'); if (t){ t.focus(); }</script>
	<?php
}

wp_print_scripts( $scripts_to_print );
?>
<script type="text/javascript">
jQuery( function( $ ) {
	$( '.hide-if-no-js' ).removeClass( 'hide-if-no-js' );
} );
</script>
</body>
</html>

wp-admin/install-helper.phpのコード

<?php
/**
 * Plugins may load this file to gain access to special helper functions for
 * plugin installation. This file is not included by WordPress and it is
 * recommended, to prevent fatal errors, that this file is included using
 * require_once.
 *
 * These functions are not optimized for speed, but they should only be used
 * once in a while, so speed shouldn't be a concern. If it is and you are
 * needing to use these functions a lot, you might experience time outs. If you
 * do, then it is advised to just write the SQL code yourself.
 *
 *     check_column( 'wp_links', 'link_description', 'mediumtext' );
 *     if ( check_column( $wpdb->comments, 'comment_author', 'tinytext' ) ) {
 *         echo "ok\n";
 *     }
 *
 *     $error_count = 0;
 *     $tablename = $wpdb->links;
 *     // Check the column.
 *     if ( ! check_column( $wpdb->links, 'link_description', 'varchar( 255 )' ) ) {
 *         $ddl = "ALTER TABLE $wpdb->links MODIFY COLUMN link_description varchar(255) NOT NULL DEFAULT '' ";
 *         $q = $wpdb->query( $ddl );
 *     }
 *
 *     if ( check_column( $wpdb->links, 'link_description', 'varchar( 255 )' ) ) {
 *         $res .= $tablename . ' - ok <br />';
 *     } else {
 *         $res .= 'There was a problem with ' . $tablename . '<br />';
 *         ++$error_count;
 *     }
 *
 * @package WordPress
 * @subpackage Plugin
 */

/** Load WordPress Bootstrap */
require_once dirname( __DIR__ ) . '/wp-load.php';

if ( ! function_exists( 'maybe_create_table' ) ) :
	/**
	 * Creates a table in the database if it doesn't already exist.
	 *
	 * @since 1.0.0
	 *
	 * @global wpdb $wpdb WordPress database abstraction object.
	 *
	 * @param string $table_name Database table name.
	 * @param string $create_ddl SQL statement to create table.
	 * @return bool True on success or if the table already exists. False on failure.
	 */
	function maybe_create_table( $table_name, $create_ddl ) {
		global $wpdb;

		foreach ( $wpdb->get_col( 'SHOW TABLES', 0 ) as $table ) {
			if ( $table === $table_name ) {
				return true;
			}
		}

		// Didn't find it, so try to create it.
		$wpdb->query( $create_ddl );

		// We cannot directly tell that whether this succeeded!
		foreach ( $wpdb->get_col( 'SHOW TABLES', 0 ) as $table ) {
			if ( $table === $table_name ) {
				return true;
			}
		}

		return false;
	}
endif;

if ( ! function_exists( 'maybe_add_column' ) ) :
	/**
	 * Adds column to database table, if it doesn't already exist.
	 *
	 * @since 1.0.0
	 *
	 * @global wpdb $wpdb WordPress database abstraction object.
	 *
	 * @param string $table_name  Database table name.
	 * @param string $column_name Table column name.
	 * @param string $create_ddl  SQL statement to add column.
	 * @return bool True on success or if the column already exists. False on failure.
	 */
	function maybe_add_column( $table_name, $column_name, $create_ddl ) {
		global $wpdb;

		foreach ( $wpdb->get_col( "DESC $table_name", 0 ) as $column ) {
			if ( $column === $column_name ) {
				return true;
			}
		}

		// Didn't find it, so try to create it.
		$wpdb->query( $create_ddl );

		// We cannot directly tell that whether this succeeded!
		foreach ( $wpdb->get_col( "DESC $table_name", 0 ) as $column ) {
			if ( $column === $column_name ) {
				return true;
			}
		}

		return false;
	}
endif;

/**
 * Drops column from database table, if it exists.
 *
 * @since 1.0.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param string $table_name  Database table name.
 * @param string $column_name Table column name.
 * @param string $drop_ddl    SQL statement to drop column.
 * @return bool True on success or if the column doesn't exist. False on failure.
 */
function maybe_drop_column( $table_name, $column_name, $drop_ddl ) {
	global $wpdb;

	foreach ( $wpdb->get_col( "DESC $table_name", 0 ) as $column ) {
		if ( $column === $column_name ) {

			// Found it, so try to drop it.
			$wpdb->query( $drop_ddl );

			// We cannot directly tell that whether this succeeded!
			foreach ( $wpdb->get_col( "DESC $table_name", 0 ) as $column ) {
				if ( $column === $column_name ) {
					return false;
				}
			}
		}
	}

	// Else didn't find it.
	return true;
}

/**
 * Checks that database table column matches the criteria.
 *
 * Uses the SQL DESC for retrieving the table info for the column. It will help
 * understand the parameters, if you do more research on what column information
 * is returned by the SQL statement. Pass in null to skip checking that
 * criteria.
 *
 * Column names returned from DESC table are case sensitive and are listed:
 *      Field
 *      Type
 *      Null
 *      Key
 *      Default
 *      Extra
 *
 * @since 1.0.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param string $table_name Database table name.
 * @param string $col_name   Table column name.
 * @param string $col_type   Table column type.
 * @param bool   $is_null    Optional. Check is null.
 * @param mixed  $key        Optional. Key info.
 * @param mixed  $default    Optional. Default value.
 * @param mixed  $extra      Optional. Extra value.
 * @return bool True, if matches. False, if not matching.
 */
function check_column( $table_name, $col_name, $col_type, $is_null = null, $key = null, $default = null, $extra = null ) {
	global $wpdb;

	$diffs   = 0;
	$results = $wpdb->get_results( "DESC $table_name" );

	foreach ( $results as $row ) {

		if ( $row->Field === $col_name ) {

			// Got our column, check the params.
			if ( ( null !== $col_type ) && ( $row->Type !== $col_type ) ) {
				++$diffs;
			}
			if ( ( null !== $is_null ) && ( $row->Null !== $is_null ) ) {
				++$diffs;
			}
			if ( ( null !== $key ) && ( $row->Key !== $key ) ) {
				++$diffs;
			}
			if ( ( null !== $default ) && ( $row->Default !== $default ) ) {
				++$diffs;
			}
			if ( ( null !== $extra ) && ( $row->Extra !== $extra ) ) {
				++$diffs;
			}

			if ( $diffs > 0 ) {
				return false;
			}

			return true;
		} // End if found our column.
	}

	return false;
}
WordPress/WordPress
WordPress, Git-ified. This repository is just a mirror of the WordPress subversion repository. Please do not send pull requests. Submit pull requests to
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