PHP Error

PHP errors can be classified into various categories based on their severity and nature. Understanding these errors is crucial for effective debugging and development. Here's a breakdown:

1. Parse Errors (Syntax Errors)

These are caused by incorrect syntax, like missing semicolons, unmatched brackets, etc. 
Example:

<?php
echo "Hello, World
?>

The above code will produce a parse error because it's missing the closing semicolon.

2. Fatal Errors

These errors halt the execution of the script. A fatal error is generally issued if PHP understands what you've asked it to do but can't perform the task. 
Example:

<?php
function greet() {
    echo "Hello, World!";
}

greetting();
?>

The above code will produce a fatal error since the function `greetting()` is not defined.

3. Warning Errors

These errors don't stop the script from continuing its execution. They're raised, for instance, when you include() a file that doesn't exist. 
Example:

<?php
include("non_existent_file.php");
echo "Hello, World!";
?>

Despite the warning, the script will continue to run and print "Hello, World!".

4. Notice Errors

These are minor errors and suggest that the script might be prone to bugs or unexpected behaviors. They do not halt the script execution. 
Example:

<?php
$var = "Hello, World!";
echo $va;
?>

The code will produce a notice since the variable `$va` is not defined.

5. Deprecated Warnings

These warnings indicate that a function or feature being used in the script is outdated and might not be supported in future versions. 
Example:

<?php
$var = split(':', 'Hello:World!');
?>

The `split()` function is deprecated, so using it will raise a deprecated warning.

Handling Errors:

PHP provides mechanisms to handle errors gracefully using `set_error_handler()`, `trigger_error()`, etc.

<?php
function customError($errno, $errstr) {
  echo "Error: [$errno] $errstr";
}

set_error_handler("customError", E_USER_WARNING);

$test=2;

if ($test>1) {
  trigger_error("Value must be 1 or below", E_USER_WARNING);
}
?>

The above script will trigger a custom error.

Reporting Levels:

You can also control what kinds of errors should be reported using `error_reporting()` function and related configurations in `php.ini`:

• `E_ALL`: All errors and warnings
• `E_ERROR`: Fatal runtime errors
• `E_WARNING`: Runtime warnings
• `E_PARSE`: Compile-time parse errors
• `E_NOTICE`: Run-time notices
• etc.

For instance:

<?php
// Report all errors
error_reporting(E_ALL);
?>

Final Thoughts: Always remember to turn off error reporting or set it to log errors instead of displaying them when moving your application from a development environment to production. Displaying errors can expose sensitive information. Always use logs in a production environment and monitor them regularly.