Curriculum

PHP Basic

PHP Intro

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PHP Install

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PHP Syntax

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PHP Comments

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PHP Variables

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PHP echo / print

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PHP Data Types

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PHP Strings

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PHP Numbers

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PHP Casting

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PHP Math

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PHP Constants

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PHP Magic Constants

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PHP Operators

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PHP if...Else...Elseif

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PHP switch

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PHP Loops

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PHP Functions

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PHP Arrays

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PHP Superglobals

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PHP RegEx

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PHP Form

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PHP Advanced

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PHP OOP

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MySQL Database

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PHP XML

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PHP Reference

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Text lesson

Error Functions

PHP Error Introduction

Error functions in PHP are used for handling and logging errors.

They enable the definition of custom error handling rules and modification of error logging methods.

Logging functions allow sending messages to other machines, emails, or system logs, while error reporting functions let you customize the level and type of error feedback provided.

Installation

The PHP error functions are built into the PHP core, so no additional installation is required to use them.

Runtime Configuration

The behavior of the error functions is influenced by settings in php.ini.

Configuration options for errors and logging:

Name	Default	Description	Changeable
error_reporting	NULL	Adjusts the error reporting level by using either an integer value or predefined named constants.	PHP_INI_ALL
display_errors	“1”	Determines whether errors should be displayed on the screen or hidden from the user. Note: This feature should only be used during development and should never be enabled on production systems.	PHP_INI_ALL
display_startup_errors	“0”	Even if `display_errors` is enabled, errors occurring during PHP’s startup sequence are not displayed. Note: It is strongly recommended to keep `display_startup_errors` turned off, except when debugging.	PHP_INI_ALL
log_errors	“0”	Specifies whether script error messages should be recorded in the server’s error log or a custom `error_log` file. Note: It is strongly recommended to use error logging rather than displaying errors on production websites.	PHP_INI_ALL
log_errors_max_len	“1024”	Defines the maximum length of `log_errors` in bytes. Setting the value to “0” means no maximum length is imposed. This length limit applies to logged errors, displayed errors, and the `$php_errormsg` variable (available since PHP 4.3).	PHP_INI_ALL
ignore_repeated_errors	“0”	Determines whether to log repeated error messages. When set to “1,” it will not log errors that occur repeatedly from the same file and line (available since PHP 4.3).	PHP_INI_ALL
ignore_repeated_source	“0”	Indicates whether to log repeated error messages. When set to “1,” it will not log errors that occur multiple times from different files or source lines (available since PHP 4.3).	PHP_INI_ALL
report_memleaks	“1”	When set to “1” (the default), this parameter will generate a report of memory leaks detected by the Zend memory manager (available since PHP 4.3).	PHP_INI_ALL
track_errors	“0”	When set to “1,” the most recent error message will always be available in the `$php_errormsg` variable.	PHP_INI_ALL
html_errors	“1”	Disables HTML tags in error messages.	PHP_INI_ALL PHP_INI_SYSTEM in PHP <= 4.2.3.
xmlrpc_errors	“0”	Disables standard error reporting and formats errors as XML-RPC error messages (available since PHP 4.1).	PHP_INI_SYSTEM
xmlrpc_error_number	“0”	Used as the value for the `faultCode` element in XML-RPC responses (available since PHP 4.1).	PHP_INI_ALL
docref_root	“”	(available from PHP 4.3)	PHP_INI_ALL
docref_ext	“”	(available from PHP 4.3.2)	PHP_INI_ALL
error_prepend_string	NULL	Defines a string to be output before an error message.	PHP_INI_ALL
error_append_string	NULL	Defines a string to be output after an error message.	PHP_INI_ALL
error_log	NULL	Specifies the file where script errors should be logged. The file must be writable by the web server’s user. If the special value `syslog` is used, errors are sent to the system logger instead.	PHP_INI_ALL

PHP Error and Logging Functions

Function	Description
debug_backtrace()	Generates a stack trace
debug_print_backtrace()	Prints a stack trace
error_clear_last()	Clears the most recent error
error_get_last()	Returns the most recent error that occurred
error_log()	Sends an error message to a log file, a specific file, or an email address.
error_reporting()	Determines which errors are reported
restore_error_handler()	Restores the previous error handler.
restore_exception_handler()	Restores the previous exception handler.
set_error_handler()	Sets a custom error handler function defined by the user.
set_exception_handler()	Sets a custom exception handler function defined by the user.
trigger_error()	Generates a user-level error message
user_error()	Alternate name for trigger_error()

PHP Predefined Error and Logging Constants

Value	Constant	Description
1	E_ERROR	Fatal run-time errors are critical errors that cannot be recovered from, leading to the immediate halting of the script’s execution.
2	E_WARNING	Run-time warnings are non-fatal errors that do not stop the script from executing.
4	E_PARSE	Compile-time parse errors are issues detected by the parser during the compilation process. These errors are specific to the parsing stage and should only be generated by the parser itself.
8	E_NOTICE	Run-time notices indicate that the script encountered something that could be an error, but it might also be a normal occurrence during script execution.
16	E_CORE_ERROR	Fatal errors at PHP startup are similar to E_ERROR, but they are generated by PHP’s core components rather than by the script itself.
32	E_CORE_WARNING	Non-fatal errors at PHP startup are akin to E_WARNING, but they originate from PHP’s core rather than from the script.
64	E_COMPILE_ERROR	Fatal compile-time errors are similar to E_ERROR, but they are produced by the Zend Scripting Engine during the compilation process.
128	E_COMPILE_WARNING	Non-fatal compile-time errors are similar to E_WARNING, but they are generated by the Zend Scripting Engine during the compilation phase.
256	E_USER_ERROR	A fatal user-generated error is similar to E_ERROR but is triggered within PHP code using the `trigger_error()` function.
512	E_USER_WARNING	A non-fatal user-generated warning is similar to E_WARNING but is created within PHP code using the `trigger_error()` function.
1024	E_USER_NOTICE	A user-generated notice is similar to E_NOTICE but is created within PHP code using the `trigger_error()` function.
2048	E_STRICT	Enable PHP to suggest changes to your code for optimal interoperability and forward compatibility. This feature has been available since PHP 5 but was not included in E_ALL until PHP 5.4.
4096	E_RECOVERABLE_ERROR	A catchable fatal error signifies that a potentially dangerous error occurred without leaving the Engine in an unstable state. If not handled by a user-defined handler, the application will abort as if it were an E_ERROR. This type of error has been available since PHP 5.2.
8192	E_DEPRECATED	Enable run-time notices to receive warnings about code that may become incompatible with future versions. This feature has been available since PHP 5.3.
16384	E_USER_DEPRECATED	A user-generated warning message is similar to E_DEPRECATED but is created within PHP code using the `trigger_error()` function. This feature has been available since PHP 5.3.
32767	E_ALL	Enable all PHP errors and warnings, except for E_STRICT in versions prior to 5.4.