Why, in PHP, are some predefined constants case-insensitive?
Why, in PHP, some predefined constants are case-insensitive (do not differentiate uppercase from Lowercase) and others are not?
Example 1:
echo __FILE__; // index.php
echo __file__; // index.php
echo __fiLE__; // index.php
Example 2:
echo PHP_EOL; \n
echo php_eol; // Use of undefined constant php_EOL - assumed 'php_eol'
echo php_EOL; // Use of undefined constant php_EOL - assumed 'php_EOL'
As it turns out, in the latter case it generates error, and in the first one it does not generate any error!
1 answers
Because it is possible to store constants in a case-insensitive way see in the documentation link
If set to TRUE, The constant will be defined case-insensitive. The default behavior is case-sensitive; i.e. CONSTANT and Constant represent different values.
Translation: if set to TRUE, the constant is set to case-insensitive. The default behavior is case-sensitive; i.e. constant and constant represent different values.
Notes: Case-insensitive constants are stored as lower-case.
Translation: case-insensitive constants are stored in low box.
Then it is possible that:
__FILE__;
__file__;
__fiLE__;
Have the same value
Constants creation command (one of them is possible to create constants with the word const).
define ('CONSTANTE' , 12, true);
define ('CONSTANTe' , 12);