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PHP offers a range of predefined constants that provide valuable information about the current runtime environment and error handling. These constants are available globally and do not require manual definition. Below are some of the most frequently used ones that are especially helpful in development and debugging scenarios.
This constant returns the current PHP version. For example:
echo PHP_VERSION; // Output: 8.1.6
Returns the name of the operating system PHP is running on. Useful for cross-platform checks.
echo PHP_OS; // Output: Linux
Returns the Server API for PHP execution. It helps determine if the script is running in CLI mode or under a web server.
echo PHP_SAPI; // Output: cli, apache2handler, cgi-fcgi, etc.
This constant returns the appropriate end-of-line symbol for the current operating system.
echo "First line" . PHP_EOL . "Second line";
Used for error reporting, this constant includes all error levels.
error_reporting(E_ALL);
Represents fatal run-time errors that cannot be recovered from.
// Constant value: 1
Indicates run-time warnings. These don't halt the script but should be addressed.
// Constant value: 2
Used for runtime notices, such as uninitialized variables. Helpful during development.
// Constant value: 8
Used for custom fatal errors triggered by the user.
// Constant value: 256
Custom user-generated warnings.
// Constant value: 512
Custom user-generated notices for debugging or information purposes.
// Constant value: 1024
Understanding and utilizing PHP's predefined constants allows developers to gain insights into the current runtime environment and improve error management. These constants are part of PHP’s core and serve as essential tools in both development and production environments.
