Letting Your Script Handle Errors In PHP

Handling and Avoiding Errors in PHP, PHP 5.6 Tutorial / By

To get flexibility, a user can create their own error handler function to deal with any errors raised when the script runs. Error handler can then inspect the error and decide what to do

  • It might log the error in a file or database.
  • Display a message to the user.
  • Attempt to fix the problem and carry on.
  • Clean up various files and database connections and exit.
  • Or ignore the error altogether.

To use own error handler tells PHP, call set_error_handler(), passing in the name of the function:

set_error_handler(“myErrorHandler”);

These are the following error types which cannot be handled by a custom error handler; instead they will always be handled by PHP’s built – in error handler:

  • E_ERROR
  • E_PARSE
  • E_CORE_ERROR
  • E_CORE_WARNING
  • E_COMPILE_ERROR
  • E_COMPILE_WARNING

In addition, most E_STRICT errors will bypass the custom error handler, if they are raised in the file where set_error_handler() is called.

A user can optionally exclude certain types of errors from being handled by the function. To do this, pass a mask as the second argument.

For example, the following code ensures that the error handler is only called for E_WARNING or E_NOTICE errors:

set_error_handler(“myErrorHandler”, E_WARNING | E_NOTICE);

The error handler function needs to have at least two parameters, as follows:

Parameter Description
Errno This parameter describes the level of the error, as an integer. This corresponds to the appropriate error level constant ( E_ERROR , E_WARNING , and so on).
Errstr This parameter describes the error message as a string.

The PHP engine passes the appropriate values to these parameters when it calls the error handler function. The function can optionally have an additional three parameters:

Parameter Description
Errfile This parameter describes the filename of the script file in which the error was raised, as a string.
Errline This parameter describes the line number on which the error was raised, as a string.
Errcontext The parameter describes an array containing all the variables that existed at the time the error was raised. It is useful for debugging.

Once it has finished dealing with the error, the error handler function should do one of three things:

    • Exit the script, if necessary. A user can do this by calling exit() or die() , passing in an optional error message or error code to return.

 

    • Return true (or nothing). If a user do this, PHP’s error handler is not called and the PHP engine attempts to continue execution from the point after the error was raised.

 

  • Return false. This causes PHP’s error handler to attempt to handle the error. This is useful if a user do no t want the error handler to deal with a particular error. Depending on the error handling settings, this usually causes the error to be logged.
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