WordPress Error handling with WP_Error class

WordPress have WP_Error class for checking WordPress errors and error messages since version 2.1.0. WordPress use object of WP_Error class for reporting error from several WP function. However, we can use this object in plugin or theme to handle error within WordPress. This class containing verious useful method for managing error.

Constructor of WP_Error allow three parameters: $code, $message and $data
Syntex is:

$error = new WP_Error( $code, $message, $data );

here, $code containing error code. it may be string or integer, $message containing error messagea and $data containing error data. however all paramater are optional.

Let we want to report new error, so we may use

$error = new WP_Error( 'not_found', 'Page Not Found', 'Page Data' );

Here, we consider not_found as error code, ‘Page Not Found’ as error message and ‘Page Data’ as error data

After creating error object we can check error by is_wp_error function.

if( is_wp_error($error) )
    echo $error->get_error_message();
//Output: Page Not Found

here, get_error_message function will get the first message available for the code. If no code is
given then the first code available will be used. If there are more then one error code in error object, then we may need to get error message by error code. In that case we may use”

echo $error->get_error_message( 'not_found' );

Here is example of using all method from WP_error class

//Creating instance of error class
$error = new WP_Error( 'not_found', 'Page Not Found', 'Page Data' );

//Add new error to object
$error->add( 'not_match', 'Field Not Match' );

//Return all error codes from object
$data = $error->get_error_codes();
print_r( $data );
//Output: Array ( [0] => not_found [1] => not_match )

//Return first error code
echo $error->get_error_code();
//Output: not_found

//Return all error message
$data = $error->get_error_messages();
print_r( $data );
//Output: Array ( [0] => Page Not Found [1] => Field Not Match )

//Return error message by error code
$data = $error->get_error_messages( 'not_match' );
print_r( $data );
//Output: Array ( [0] => Field Not Match )

//Return first error message if no code are given
echo $error->get_error_message();
//Output: Page Not Found

//Return first error message for given error code
echo $error->get_error_message( 'not_match' );
//Output: Field Not Match

//Return first error data
echo $error->get_error_data();
//Output: Page Data

//Return error data from error code.
echo $error->get_error_data( 'not_found' );
//Output: Page Data

//add error data to error code
//syntex: add_data( $data, $code );
$error->add_data( 'Some data', 'not_match' );
echo $error->get_error_data( 'not_match' );
//Output: Some data

//Check whether variable is a WordPress Error.
//return bool True, if WP_Error. False, if not WP_Error.
$data = is_wp_error( $error );
var_dump( $data );
//Output: bool(true)

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