PHP Error Handling user_error() Function

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The PHP Error Handling user_error() function is used to generate a user-defined error message. It is used to display an error message when a user-specified condition is met. It can be used in combination with the built-in error handler or a user-defined function defined using the set_error_handler() method.

When you want to execute a script dynamically with a user-defined message to a given condition, this function is very useful. This function returns TRUE otherwise, and FALSE if an invalid error type is specified.

This function works the same as the trigger_error() function.

Syntax

Below is the syntax of the PHP Error Handling user_error() function −

bool user_error ( string $error_msg [, int $error_type] );

Parameters

Here are the parameters of the user_error() function −

• $error_msg − (Required) It specifies the error message. Limited to 1024 characters in length.

• $error_types − (Optional) It specifies the error type for this error message. Possible error types −

  • E_USER_ERROR − Fatal user-generated run-time error. Errors that can not be recovered from. Execution of the script is halted.

  • E_USER_WARNING − Non-fatal user-generated run-time warning. Execution of the script is not halted.

  • E_USER_NOTICE − Default. User-generated run-time notice. The script found something that might be an error, but could also happen when running a script normally.

Return Value

The user_error() function returns TRUE on success. And FALSE if wrong error_type is specified.

PHP Version

First introduced in core PHP 4, the user_error() function continues to function easily in PHP 5, PHP 7, and PHP 8.

Example 1

This program demonstrates the simple use of the PHP Error Handling user_error() function to display a user-defined warning message. It starts an informational message that is not necessary that does not stop the script.

<?php
    // Display a simple notice 
    $message = "This is a user-defined notice.";
    user_error($message, E_USER_NOTICE);

    echo "Script continues after the notice.";
?>

Output

Here is the outcome of the following code −

Notice: This is a user-defined notice.
Script continues after the notice.

Example 2

This program shows how to generate a warning with the help of the user_error() function. The warning is displayed to the user, but the script will still run. Basically we are using the optional parameter $error_types E_USER_WARNING which is used to given user generated run time error.

<?php
    // Trigger a warning 
    $age = 15;
    if ($age < 18) {
        user_error("Warning: Age must be 18 or older to proceed.", E_USER_WARNING);
    }

    echo "Script continues after the warning.";
?> 

Output

This will generate the below output −

Warning: Warning: Age must be 18 or older to proceed. 
Script continues after the warning.

Example 3

Now the below code uses the E_USER_ERROR inside the user_error() method, and create a critical error message. The program execution stops when the error is triggered.

<?php
    // Trigger a fatal error
    $divisor = 0;
    if ($divisor == 0) {
        user_error("Error: Division by zero is not allowed.", E_USER_ERROR);
    }

    // This line will not execute because of the fatal error
    echo "This message won't be displayed.";
?> 

Output

This will create the below output −

Error: Division by zero is not allowed.

Example 4

In the following example, we are using the user_error() function and combining it with a custom error handler. This program uses user_error() function to handle errors in a user-defined way and set_error_handler() to set a custom error handler.

<?php
    // Custom error handler function
    function customErrorHandler($errno, $errstr) {
    echo "Custom Error [$errno]: $errstr\n";
    return true;
    }

    // Set the custom error handler
    set_error_handler("customErrorHandler");

    // Triggering a user-defined error
    user_error("This is a custom-handled error.", E_USER_WARNING);

    echo "Script continues after custom error handling.";
?> 

Output

Following is the output of the above code −

Custom Error [512]: This is a custom-handled error.
Script continues after custom error handling.