Error map
Cannot redeclare Fatal error: Cannot redeclare function foo() (previously declared in …)
PHP · 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)
WordPress: There Has Been a Critical Error on This Website
A PHP fatal error (usually from a plugin or theme) stopped WordPress; the real error is in the debug log or recovery-mode email.
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.
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.
Fatal error: Uncaught mysqli_sql_exception
A MySQLi query or connection failed; since PHP 8.1 MySQLi throws exceptions by default.
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.
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 DivisionByZeroError: Division by zero
Code divided by zero (or used modulo by zero) — PHP 8 throws instead of warning.
PHP Fatal error: Maximum execution time of 30 seconds exceeded
The script ran longer than `max_execution_time` and PHP stopped it.
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.
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.
PHP Fatal error: Allowed memory size of X bytes exhausted
The script tried to use more memory than PHP’s `memory_limit` allows.
Fatal error: Uncaught Exception: message in file.php:12
An exception was thrown and nothing caught it, so PHP stopped the script.
Two steps away (35)
HTTP 500 Internal Server Error
The server hit an unexpected condition — usually an unhandled exception or misconfiguration in the application.
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.
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.
PDOException: could not find driver
The PDO driver for your database (pdo_mysql, pdo_pgsql, pdo_sqlite) isn’t installed or enabled.
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.
MySQL ERROR 1062 (23000): Duplicate entry for key
An INSERT/UPDATE would create a duplicate value in a PRIMARY or UNIQUE key.
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…
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.
Warning: Array to string conversion
An array was used where a string is expected — echoing it, concatenating it, or passing it to a string function.
Fatal error: Uncaught Error: Cannot use object of type stdClass as array
Code used array syntax (`$x['key']`) on an object.
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).
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.
java.lang.NullPointerException
Code called a method or accessed a field on a reference that is `null`.
Composer: PHP Fatal error: Allowed memory size of 1610612736 bytes exhausted
Composer ran out of memory while resolving or installing dependencies.
SQL Error: division by zero / Divide by zero error encountered
An expression divided by a value that was 0 for at least one row.
ZeroDivisionError: division by zero
A number was divided (or modulo’d) by zero.
HTTP 504 Gateway Timeout
A proxy or gateway waited too long for the upstream server to respond and gave up.
Cloudflare Error 524: A Timeout Occurred
Cloudflare connected to the origin, but the origin didn’t send an HTTP response within 100 seconds.
WordPress: The link you followed has expired
Usually an upload (theme, plugin, media) larger than PHP’s upload/post limits — WordPress receives an empty request and shows thi…
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).
FastCGI sent in stderr: "Primary script unknown"
Nginx passed a script path to PHP-FPM that PHP-FPM couldn’t find — usually a wrong SCRIPT_FILENAME or root.
ERROR: function x(text) does not exist — No function matches the given name and argument types
PostgreSQL found no function with that name and argument types — wrong types, missing extension, or schema not in search_path.
Error: ENOENT: no such file or directory
A file or directory the program tried to open doesn’t exist at that path.
Linux: Permission denied
Your user (or the service user) lacks read/write/execute permission on a file, directory or one of its parents.
java.io.FileNotFoundException: config.properties (No such file or directory)
Java couldn’t open the file — wrong path relative to the working directory, missing file, or a classpath resource read as a file.
Kubernetes: OOMKilled (exit code 137)
The container used more memory than its limit, and the kernel killed it.
HTTP 413 Content Too Large (Request Entity Too Large)
The request body is bigger than the server is willing to accept — usually a file upload over the configured limit.
java.lang.OutOfMemoryError: Java heap space
The JVM ran out of heap memory and garbage collection couldn’t free enough.
java.lang.IllegalStateException
A method was called when the object wasn’t in the right state for it.
java.lang.ArithmeticException: / by zero
Integer division or modulo by zero.
java.util.NoSuchElementException: No value present
Code asked for an element that doesn’t exist — Optional.get() on empty, iterator.next() past the end, Scanner with no input.
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