dead_db()
- Since
- 2.3.2
- Source
wp-includes/functions.php:5493
Description
If a file exists in the wp-content directory named db-error.php, then it will be loaded instead of displaying the WordPress DB error. If it is not found, then the WordPress DB error will be displayed instead.
The WordPress DB error sets the HTTP status header to 500 to try to prevent search engines from caching the message. Custom DB messages should do the same.
This function was backported to WordPress 2.3.2, but originally was added in WordPress 2.5.0.
Compatibility
- WordPress
- since 2.3.2
- PHP
- 7.4–8.6-dev
- 6.7.7
- 6.8.8
- 6.9.7
- 7.0.4
- 7.1.0
Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.
Performance profile
How much work a call to dead_db() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.
- Cost class
- Heavy
- Scaling
- Constant
- Instructions
- 27–37
- Plugin surface
- None
- Called by
- 4
Reads or writes the filesystem via file_exists().
No loop in the body: the same number of instructions runs whatever you pass in.
Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 37.
Nothing here hands control to plugin code.
4 places in core call this, so the cost is paid more often than your own code shows.
What it touches
- filesystemfilesystem access
file_exists()called directly - hookthird-party callbacks
apply_filters()one call below dead_db()
Further down the call graph this can also reach query, option, cache, serialize and transient. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.
What one call costs · 4 distinct outcomes
One number would be a lie: the work depends on which branch runs. These are every distinct cost dead_db() can have, taken from its control-flow graph on PHP 8.5.
| When | Instructions | Calls it makes |
|---|---|---|
!file_exists() && !wp_installing() && !defined('WP_ADMIN') | 27 | wp_load_translations_early(), file_exists(), wp_installing(), __(), __(), wp_die() |
!file_exists() | 30–32 | wp_load_translations_early(), file_exists(), wp_installing(), wp_die(), __(), __(), wp_die() |
file_exists() && !wp_installing() && !defined('WP_ADMIN') | 32 | wp_load_translations_early(), file_exists(), exit(), wp_installing(), __(), __(), wp_die() |
file_exists() | 35–37 | wp_load_translations_early(), file_exists(), exit(), wp_installing(), wp_die(), __(), __(), wp_die() |
Across PHP versions
| PHP | Compiled | Executed | Branches | Notes |
|---|---|---|---|---|
| 8.6-dev | 37 | 27–37 | 3 | |
| 8.5 | 37 | 27–37 | 3 | |
| 8.4 | 37 | 27–37 | 3 | 1 more instruction than PHP 8.3 |
| 8.3 | 36 | 13–32 | 3 | |
| 8.2 | 36 | 13–32 | 3 | |
| 8.1 | 36 | 13–32 | 3 | |
| 7.4 | 36 | 13–32 | 3 |
An instruction is not a fixed amount of time, so a matching count is not necessarily the same speed; what it rules out is a difference in the work itself.
Uses · 4
- wp_load_translations_early()Attempts an early load of translations.
- wp_installing()Checks or sets whether WordPress is in "installation" mode.
- wp_die()Kills WordPress execution and displays HTML page with an error message.
- __()Retrieves the translation of $text.
Used by · 4
- is_blog_installed()Determines whether WordPress is already installed.
- ms_not_installed()Displays a failure message.
- wp_set_wpdb_vars()Sets the database table prefix and the format specifiers for database table columns.
- wpdb::check_connection()Checks that the connection to the database is still up. If not, try to reconnect.
Source code
function dead_db() { global $wpdb; wp_load_translations_early(); // Load custom DB error template, if present. if ( file_exists( WP_CONTENT_DIR . '/db-error.php' ) ) { require_once WP_CONTENT_DIR . '/db-error.php'; die(); } // If installing or in the admin, provide the verbose message. if ( wp_installing() || defined( 'WP_ADMIN' ) ) { wp_die( $wpdb->error ); } // Otherwise, be terse. wp_die( '<h1>' . __( 'Error establishing a database connection' ) . '</h1>', __( 'Database Error' ) );}Changelog
Introduced in 2.3.2. One change between 6.7.7 and 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
none to never.verified against sourceAbout this page
- Parsed data
- Generated from the wordpress-develop 6.8.8 tag, from
src/wp-includes/functions.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it. - Corrections
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