In PHP, line breaks can be replaced with PHP_EOL to improve source-code portability of the code:
  • Unix systems use \n
  • Windows systems use \r\n
  • Mac uses \r
<?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";
?>