Description of PHP_EOL DIRECTORY_SEPARATOR constant_PHP tutorial

PHP_EOL Description of the DIRECTORY_SEPARATOR constant

PHP_EOL is a newline character constant defined in the PHP system source code.

Why is there such a constant?

Because the newline characters are different in different systems. For example:

For unix series n

For windows series rn

r for mac

So PHP_EOL is defined in PHP. This constant will change according to the platform to improve the source code level portability of the code.

<?php
echo PHP_EOL;
//windows平台相当于   
echo "\r\n";
//unix\linux平台相当于   
echo "\n";
//mac平台相当于   
echo "\r";

Similar and commonly used ones are

DIRECTORY_SEPARATOR

PHP’s built-in constant DIRECTORY_SEPARATOR is a command that displays the system separator and can be used directly without any definition or inclusion.

As we all know, the path separator under Windows is (of course / can also run normally on some systems), and the path separator on Linux is /, which leads to a problem. For example, the development machine is Windows, there is an image upload program, the designated upload file saving directory on the debugging machine is:

define('ROOT', dirname(__FILE__)."\upload");

It is normal to debug locally, but an error will occur after uploading to the Linux server. Therefore, the strict writing method of the above code is:

define('ROOT', dirname(__FILE__).DIRECTORY_SEPARATOR."upload");

Tip: You can use the function get_defined_constants() to get all PHP constants, for example:

<?php
print_r(get_defined_constants());//get_defined_constants()返回所有常量数组

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