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# Predefined constants

The predefined constants (always available) are:

__FILE__ (case-insensitive)

  The name of the script file presently being parsed. If used within a file which has been included or required, then the name of the included file is given, and not the name of the parent file.

__LINE__ (case-insensitive)

  The number of the line within the current script file which is being parsed. If used within a file which has been included or required, then the position within the included file is given.

PHP_VERSION

  The string representation of the version of the PHP parser presently in use; for example '4.1.0'.

PHP_OS

  The name of the operating system on which the PHP parser is executing;. Possible values may be : "AIX", "Darwin" (MacOS), "Linux", "SunOS", "WIN32", "WINNT". Note: other values may be available too.

`TRUE` (case-insensitive)

  A `TRUE` value (see the boolean type).

`FALSE` (case-insensitive)

  A `FALSE` value (see the boolean type).

`NULL` (case-insensitive)

  A `NULL` value (see the null type).

E_ERROR

  Denotes an error other than a parsing error from which recovery is not possible.

E_WARNING

  Denotes a condition where PHP knows something is wrong, but will continue anyway; these can be caught by the script itself. An example would be an invalid regexp in ereg().

E_PARSE

  The parser choked on invalid syntax in the script file. Recovery is not possible.

E_NOTICE

  Something happened which may or may not be an error. Execution continues. Examples include using an unquoted string as an array index, or accessing a variable which has not been set.

E_ALL

  All of the E_* constants rolled into one. If used with error_reporting(), will cause any and all problems noticed by PHP to be reported.

The `E_*` constants are typically used with the error_reporting() function for setting the error reporting level. See all these constants at Error handling.

Example 8-2. Using __FILE__ and __LINE__
    <?php
    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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