PHP Predefined Constants
PHP has nine predefined constants that change value depending on where they are used, and therefor they are called "magic constants".
These magic constants are written with a double underscore at the start and the end, except for the ClassName::class constant.
Magic Constants
Here are the magic constants, with descriptions and examples:
| Constant |
Description |
|
| __CLASS__ |
If used inside a class, the class name is returned. |
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| __DIR__ |
The directory of the file. |
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| __FILE__ |
The file name including the full path. |
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| __FUNCTION__ |
If inside a function, the function name is returned. |
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| __LINE__ |
The current line number. |
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| __METHOD__ |
If used inside a function that belongs to a class, both class and function name is returned. |
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| __NAMESPACE__ |
If used inside a namespace, the name of the namespace is returned. |
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| __TRAIT__ |
If used inside a trait, the trait name is returned. |
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| ClassName::class |
Returns the name of the specified class and the name of the namespace, if any. |
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Note:
The magic constants are case-insensitive, meaning __LINE__ returns the same as __line__.
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