Error map
Critical error WordPress: There Has Been a Critical Error on This Website
WordPress · layer 4, Application & API
Centre: this error. First ring: errors it is linked with (12). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (12)
HTTP 500 Internal Server Error
The server hit an unexpected condition — usually an unhandled exception or misconfiguration in the application.
PHP Parse error: syntax error, unexpected …
PHP can’t parse the file because of a syntax mistake — the real error is often on the line before the one reported.
PHP Fatal error: Uncaught Error: Call to undefined function
PHP can’t find the function you called — usually a missing extension, missing include, or namespace issue.
WordPress: Error Establishing a Database Connection
WordPress can’t connect to its MySQL/MariaDB database with the credentials in wp-config.php, or the database server is down.
WordPress: Briefly unavailable for scheduled maintenance. Check back in a minute.
An update was interrupted and WordPress left its `.maintenance` file behind, so the site stays in maintenance mode.
Fatal error: Uncaught Error: Call to a member function x() on null
Code called a method on a variable that is null instead of an object.
Fatal error: Uncaught ArgumentCountError: Too few arguments to function foo(), 1 passed and exactly 2 expected
A function was called with fewer arguments than it requires.
WordPress: Fatal error: Uncaught Error: Call to undefined function wp_get_current_user() / add_action() / get_header()
Code called a WordPress function before WordPress loaded, or a theme/plugin file was opened directly.
WordPress on PHP 8: Fatal error: Uncaught Error: Call to undefined function create_function() / each()
An old plugin/theme uses functions removed in PHP 8 (create_function, each), so the site breaks after a PHP upgrade.
WordPress: Updating failed. The response is not a valid JSON response.
The block editor saved via the REST API but got HTML or an error page back — broken permalinks, a security plugin/WAF, or PHP out…
Fatal error: Cannot redeclare function foo() (previously declared in …)
The same function (or class) was defined twice — usually a file included more than once.
WordPress: Installation failed: Could not create directory (plugin/theme install or update)
WordPress can’t write to wp-content/plugins, themes or upgrade — ownership/permissions or disk space.
Two steps away (36)
HTTP 404 Not Found
The server can’t find anything at the requested URL.
HTTP 502 Bad Gateway
A proxy or gateway (Nginx, load balancer, CDN) got an invalid response — or no response — from the upstream server behind it.
HTTP 503 Service Unavailable
The server is temporarily unable to handle the request — overloaded, in maintenance, or has no healthy backends.
MySQL ERROR 1064 (42000): You have an error in your SQL syntax
MySQL couldn’t parse the query. The text after “near” shows where parsing failed.
IndentationError: unexpected indent / expected an indented block
Python’s block structure is broken — inconsistent indentation or mixed tabs and spaces.
SyntaxError: invalid syntax
Python couldn’t parse the code. The caret (^) points at or just after the mistake.
PHP Fatal error: Uncaught Error: Class "X" not found
PHP couldn’t load the class — autoloading failed, the namespace is wrong, or the dependency isn’t installed.
Warning: Cannot modify header information - headers already sent
You called `header()`, `setcookie()` or `session_start()` after output had already been sent to the browser.
Fatal error: Uncaught TypeError: foo(): Argument #1 ($x) must be of type int, string given
A function received a value of the wrong type for a typed parameter.
MySQL ERROR 1045 (28000): Access denied for user
MySQL rejected the login — wrong password, wrong user/host combination, or the user doesn’t exist.
MySQL ERROR 2002 (HY000): Can't connect to local MySQL server through socket
The client couldn’t reach the MySQL server — it isn’t running, or the client is looking for the socket/port in the wrong place.
MySQL ERROR 1040 (08004): Too many connections
MySQL reached `max_connections` and refuses new clients.
PHP Fatal error: Maximum execution time of 30 seconds exceeded
The script ran longer than `max_execution_time` and PHP stopped it.
warning: There are too many unreachable loose objects; run 'git prune' to remove them.
Git’s automatic garbage collection found many unreachable objects and is asking you to prune.
WordPress: Missed schedule — scheduled posts not publishing (WP-Cron not running)
WP-Cron didn’t fire at the scheduled time, so scheduled posts and tasks (backups, emails, WooCommerce jobs) are late.
System.NullReferenceException: Object reference not set to an instance of an object
Code dereferenced a variable that is `null` — the .NET equivalent of Java’s NullPointerException.
PHP Fatal error: Allowed memory size of X bytes exhausted
The script tried to use more memory than PHP’s `memory_limit` allows.
java.lang.NullPointerException
Code called a method or accessed a field on a reference that is `null`.
Fatal error: Uncaught DivisionByZeroError: Division by zero
Code divided by zero (or used modulo by zero) — PHP 8 throws instead of warning.
Fatal error: Uncaught mysqli_sql_exception
A MySQLi query or connection failed; since PHP 8.1 MySQLi throws exceptions by default.
Composer: PHP Fatal error: Allowed memory size of 1610612736 bytes exhausted
Composer ran out of memory while resolving or installing dependencies.
Fatal error: Maximum function nesting level of '256' reached, aborting!
Recursion went deeper than Xdebug’s max_nesting_level allows (or PHP crashed with a segfault without Xdebug).
Fatal error: Uncaught Error: Cannot use object of type stdClass as array
Code used array syntax (`$x['key']`) on an object.
To perform the requested action, WordPress needs to access your web server. Please enter your FTP credentials to proceed
WordPress can’t write directly to its files (ownership differs from the PHP user), so it falls back to asking for FTP details.
Deprecated: strlen(): Passing null to parameter #1 ($string) of type string is deprecated
PHP 8.1+ warns when null is passed to a built-in function that expects a string/int.
Deprecated: Creation of dynamic property Foo::$bar is deprecated
PHP 8.2+ deprecates creating properties that aren’t declared in the class.
Fatal error: Uncaught TypeError: Unsupported operand types: string + int
An arithmetic or array operator was used with incompatible types (PHP 8 is stricter than PHP 7).
HTTP 403 Forbidden
The server understood the request but refuses to authorize it — you (or the server process) are not allowed to access this resour…
SyntaxError: Unexpected token < in JSON at position 0
`JSON.parse()` / `response.json()` received something that isn’t JSON — very often an HTML error page.
WordPress: Are you sure you want to do this? Please try again. (nonce check failed)
A WordPress security nonce didn’t validate — the page was open too long, cached, or a plugin/theme form is broken.
Warning: include(x.php): Failed to open stream: No such file or directory
PHP couldn’t open a file for include/require/fopen — wrong path, missing file, or no permission.
Fatal error: Uncaught Exception: message in file.php:12
An exception was thrown and nothing caught it, so PHP stopped the script.
WordPress: Plugin could not be activated because it triggered a fatal error
Activating the plugin caused a PHP fatal error — usually PHP version incompatibility, a conflict with another plugin/theme, or mi…
Linux: Permission denied
Your user (or the service user) lacks read/write/execute permission on a file, directory or one of its parents.
WordPress: Unable to create directory wp-content/uploads/2026/10. Is its parent directory writable by the server?
PHP can’t write to wp-content/uploads — wrong ownership/permissions, a wrong upload path, full disk, or open_basedir restrictions.
WordPress: Destination folder already exists. Plugin installation failed
A folder with the plugin/theme’s name already exists in wp-content, usually from a failed or partial previous install.
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