Error map
Call to undefined function PHP Fatal error: Uncaught Error: Call to undefined function
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)
HTTP 500 Internal Server Error
The server hit an unexpected condition — usually an unhandled exception or misconfiguration in the application.
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.
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 DivisionByZeroError: Division by zero
Code divided by zero (or used modulo by zero) — PHP 8 throws instead of warning.
Fatal error: Uncaught Exception: message in file.php:12
An exception was thrown and nothing caught it, so PHP stopped the script.
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.
Class "NumberFormatter" not found / The "intl" PHP extension is required
Code uses the intl extension (NumberFormatter, Collator, IntlDateFormatter) but it isn’t installed.
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.
Fatal error: Cannot redeclare function foo() (previously declared in …)
The same function (or class) was defined twice — usually a file included more than once.
Two steps away (33)
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.
PHP Fatal error: Allowed memory size of X bytes exhausted
The script tried to use more memory than PHP’s `memory_limit` allows.
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.
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.
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.
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…
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).
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.
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.
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: Maximum execution time of 30 seconds exceeded
The script ran longer than `max_execution_time` and PHP stopped it.
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.
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.
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.
PDOException: could not find driver
The PDO driver for your database (pdo_mysql, pdo_pgsql, pdo_sqlite) isn’t installed or enabled.
Fatal error: Uncaught Error: Call to undefined function imagecreatefromjpeg()
The GD extension (or its JPEG/WebP support) isn’t installed for the PHP version serving the site.
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.
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.
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.
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.
The package could not be installed. No valid plugins were found
The uploaded zip doesn’t contain a plugin main file with a plugin header at the expected level — often a zip of zips, a theme, or…
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.
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