trigger_error(): Generates a user-level error/warning/notice message

<?Php
$price_sell=100;
$price_buy=120;
if($price_sell<=$price_buy){
 trigger_error("Do you want to sell without profit?");
}
?>

Notice: Do you want to sell without profit? in C:\xampp\htdocs\t\checking.php on line 5

trigger_error("Do you want to sell without profit?",E_USER_ERROR);

Fatal error: Do you want to sell without profit? in C:\xampp\htdocs\t\checking.php on line 5

trigger_error("Do you want to sell without profit?",1024);

Notice: Do you want to sell without profit? in C:\xampp\htdocs\t\checking.php on line 5

trigger_error(string $message, int $error_level = E_USER_NOTICE)

Example 2: Triggering Different Error Levels

You can specify the type of error you want to generate using different constants:

trigger_error("This is a warning.", E_USER_WARNING); // User warning
trigger_error("This is an error.", E_USER_ERROR); // User error
trigger_error("This is a notice.", E_USER_NOTICE); // User notice

Example 3: Using trigger_error() in a try-catch Block

You can handle custom errors inside a try-catch block for better control:

set_error_handler(function($errno, $errstr) {
    throw new ErrorException($errstr, $errno);
});
try {
    trigger_error("Custom error.", E_USER_ERROR);
} catch (Exception $e) {
    echo "Caught exception: " . $e->getMessage();
}

Use Case: Validation Error with trigger_error()

Use *trigger_error()* in form validation to display custom error messages for invalid inputs:

$age = -5;
if ($age < 0) {
    trigger_error("Age cannot be negative.", E_USER_WARNING);
}

Example 4: Combining trigger_error() with error_log()

You can log errors to a file for later analysis:

ini_set("log_errors", 1);
ini_set("error_log", "/path/to/error.log");
trigger_error("Logging this error.", E_USER_NOTICE);

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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