Getting Started with PHP: Define using _php Tutorials

PHP defines several constants in advance and provides a mechanism to define them at run time. Constants and variables are basically the same, and the difference is that constants must be defined with the Define function, which, once defined, cannot be redefined.

Pre-defined constants in PHP:

__file__

The file name of the script currently being processed. If used in a contained file, then its value is the contained file, not the file name that contains it.

__line__

The current number of rows in the file being processed.

Php_version

Represents the current version of the PHP processor, such as: 3.0.8-dev.

Php_os

The name of the operating system on which the PHP processor is located, such as: Linux.

TRUE

Truth

FALSE

False value

You can define more constants with the Define function.

For example, define constants:

Define ("CONSTANT", "Hello World");
Echo CONSTANT; Outputs "Hello world."
?>

Examples of using __file__ and __line__

function Report_error ($file, $line, $message) {
echo "An error occured in $file on line $line: $message.";
}
Report_error (__file__,__line__, "Something went wrong!");
?>

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