(PHP 4, PHP 5, PHP 7, PHP 8)
chdir — 改变目录
directory新的当前目录
   Throws an error of level E_WARNING on failure.
  
示例 #1 chdir() 例子
<?php
// current directory
echo getcwd() . "\n";
chdir('public_html');
// current directory
echo getcwd() . "\n";
?>以上示例的输出类似于:
/home/vincent /home/vincent/public_html
    If the PHP interpreter has been built with ZTS (Zend Thread Safety) enabled,
    any changes to the current directory made through chdir()
    will be invisible to the operating system. All built-in PHP functions will
    still respect the change in current directory; but external library
    functions called using FFI will not. You
    can tell whether your copy of PHP was built with ZTS enabled using
    php -i or the built-in constant
    PHP_ZTS.