PHP | Predefined Exceptions

Predefined exceptions are available in PHP for more efficient exception handling but prerequisite to this article is learning exception handling https://www.geeksforgeeks.org/exception-handling-in-php/  

Exception: This feature is available in PHP version 5 and 7. In version 7, it behaves a base class for every user-defined exception, but in version 5, it behaves a base class for every exception present.

There are 10 methods and 4 properties of the Exception class.

The four properties are –

Short description	data type	Full description
message	string	The message to be displayed when an exception occurs.
code	int	The code of the exception when an exception occurs.
file	string	The name of the file in which exception occurs.
line	int	The number of the line in which exception occurs.

The ten methods in Exception are

Function name	number of arguments	name of arguments	return type	description
__construct	3	message (string) code (int) previous(throwtable)	void	an exception is constructed
getMessage	0	void	string	returns the message to be displayed when exception occurs
getPrevious	0	void	throwtable	previous exceptions are returned
getCode	0	void	mixed	The code for exception generated
getFile	0	void	string	The file in which exception occurs in returned
getLine	0	void	int	The number line in which exception occurs returned
getTrace	0	void	array	The stack trace is returned
getTraceAsString	0	void	string	The stack trace is returned in the form of string
__toString	0	void	string	The exception generated is returned in the form of string
__clone	0	void	void	The exception generated is cloned

ErrorException: The ErrorException class is just an extended version of the Exception class. It has only one new added property, rest have been inherited from the Exception class. There are two new additional methods, one for construction of exception and the second which returns the severity of the exception occurred.

The additional one properties are –

Short description	Data type	Full description
severity	int	for indicating severity of the exception occurred.

The additional to methods are –

Function name	number of arguments	name of argument	return type	description
__construct	6	message (string) code (int) severity (int) file name (string) line number (int) previous exception (throwtable)	void	an exception is constructed
getSeverity	0	void	int	the function returns severity of the exception

Error: All the internal errors getting generated in PHP are from this base class. It has similar features like Exception class. It has four properties and ten methods. The function name are the same and the properties are all the same. The difference in these two classes is that the Exception class methods return information about the exception and Error class returns information about internal errors in PHP.

ArgumentCountError: It comes into use when the expected number of arguments are not passed to a user-defined function as parameters. It is an extension of TypeError class where all the methods and properties have been inherited from it.

ArithmeticError: When arithmetic calculations are being performed in PHP and an exception occurs then this class is brought into use. In PHP version 7, when such type of error occurs negative value bit shifting is also attempted. This class is an extension of class Error and hence all the methods are properties that have just been inherited from the class Error.

AssertionError: If an assertion has been performed through the function assert and it results in an exception then this class comes into use. The function assert() is used to calculate assertion and this function returns a Boolean value. This function is a helpful feature when it comes to debugging.

DivisionByZeroError: If a number is being divided by zero, then this class is used which is an extension of class ArithmeticError.

CompileError: If errors occur during compilation then compilation errors occur which class CompileError class. Normally compilation errors are fatal errors. This class is an extension of class Error.

ParseError: When PHP code is being parsed and an exception occurs, this class comes into use. It is an extension of class CompileError. Function like eval() which is a language construct generates this type of exception.

TypeError: This class is an extension of class Error. There are three main reasons for the generation of such type of exception.

• The parameter type declared in the function doesn’t match the type of the arguments being passed.
• The return type of function that was declared doesn’t match the type which is being returned.
• There are some built-in PHP functions which take restricted and certain type of parameters. If the wrong type or number of arguments is passes to them this exception occurs.