PHP
The Exception class
Learn the Exception class's getMessage(), getCode() and getTrace() methods.
Methods of the Exception class
The Exception object carries information about the error. You use five common methods.
getMessage() returns the message, getCode() returns the error code. getFile() and getLine() show where the error was thrown. getTrace() returns the call stack as an array.
You call them in the catch block to report the error or write it to a log.
The code and the second argument
The second argument to the Exception constructor is a numeric code: new Exception('Unauthorized', 403). This code can be an HTTP status, an error number or any application-defined value.
In the catch block you read it with $e->getCode(). The code is useful to distinguish errors programmatically; the message is for humans and is shown directly.
Exercise Print the exception details
Inside a try block, throw new Exception("Invalid user", 403). In the catch (Exception $e) block, print getMessage() and getCode() on separate lines.
Show example solution
Inside try, call throw new Exception("Invalid user", 403). In catch (Exception $e), write echo $e->getMessage() . "\n"; and echo $e->getCode() . "\n";.
Example solution:
<?php
// Throw an exception and print getMessage/getCode
try {
throw new Exception("Invalid user", 403);
} catch (Exception $e) {
echo $e->getMessage() . "\n";
echo $e->getCode() . "\n";
}
Test yourself
-
Match the methods
- getMessage()
- Returns the message
- getCode()
- Returns the code
- getTrace()
- Returns the call stack
- getFile()
- Returns the file name
-
Read the code
<?php
try {
throw new Exception("Error", 42);
} catch (Exception $e) {
echo $e->____();
}
Show answer
<?php
try {
throw new Exception("Error", 42);
} catch (Exception $e) {
echo $e->getCode();
}
-
What does 42 mean in new Exception('Error', 42)?
- The error code
- The error line number
- The error file
- The error priority
Show answer
The error code — Correct. 42 is the second argument to the Exception constructor; it is read with getCode().
Next lesson: error_reporting configuration
