有什么比 require('myParent.php') 更好的 require(dirname(__FILE__).'/'.'myParent.php') 呢？
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What's better of require(dirname(__FILE__).'/'.'myParent.php') than just require('myParent.php')?
提问by datasn.io
Lots of famous PHP scripts including WordPress use dirname(__FILE__).'/myParent.php'instead of just 'myParent.php'when including files in the same directory of the currently running script.
许多著名的 PHP 脚本（包括 WordPress）都在使用，dirname(__FILE__).'/myParent.php'而不仅仅是'myParent.php'将文件包含在当前运行的脚本的同一目录中。
Aren't they the same thing? Why do you prefer typing more?
他们不是一回事吗？为什么你更喜欢打字？
Thanks.
谢谢。
回答by Gumbo
PHP needs to know the absolute path to the file. dirname(__FILE__).'/myParent.php'already is the absolute path but 'myParent.php'requires a lookup using the given paths in include_pathto get an absolute path and find the file. A better choice would be './myParent.php':
PHP 需要知道文件的绝对路径。dirname(__FILE__).'/myParent.php'已经是绝对路径，但'myParent.php'需要使用include_path 中的给定路径进行查找以获取绝对路径并找到文件。更好的选择是'./myParent.php'：
However, it is more efficient to explicitly use
include './file'than having PHP always check the current directory for every include.
然而，显式使用
include './file'比让 PHP 总是检查当前目录中的每个包含更有效。
回答by Justin Johnson
Besides the performance increase (which is likely a pre-optimization in most cases*), it also protects from the (very odd) scenario where the environment's PHP configuration does not have the current directory (.) as part of the include path.
除了性能提升（在大多数情况下这可能是预先优化*），它还可以防止环境的 PHP 配置没有将当前目录 ( .) 作为包含路径的一部分的（非常奇怪的）场景。
* Benchmark of includeusing a path that requires include_pathlookup versus a relative path that does not. Tested over 100000 iterations each
*include使用需要include_path查找的路径与不需要查找的相对路径的基准。每次测试超过 100000 次迭代
Results
结果
include("include.php"): 8.3664200305939s
include("./include.php"): 8.3511519432068s
(8.3664200305939 - 8.3511519432068) / 100000 = 0.000000152680874s
Unless you're including hundreds or thousands of files, 0.0000001s is negligible at best.
除非您包含数百或数千个文件，否则 0.0000001s 充其量可以忽略不计。
Test code
测试代码
define("MAX", 100000);
ob_start();
$i = MAX;
$_t = microtime(true);
do {
include("include.php");
} while ( --$i );
$_t = microtime(true) - $_t;
ob_end_clean();
echo "include(\"include.php\"): {$_t}s\n";
ob_start();
$i = MAX;
$_t = microtime(true);
do {
include("./include.php");
} while ( --$i );
$_t = microtime(true) - $_t;
ob_end_clean();
Test was conducted on a 2.16GHz Macbook 10.5.8 with PHP Version 5.2.9 (www.entropy.ch Release 7)
测试在 2.16GHz Macbook 10.5.8 和 PHP 版本 5.2.9 (www.entropy.ch Release 7) 上进行
回答by alexef
Using dirname + file name is slightly faster, because PHP will not iterate through include_pathsearching for the file. If speed matters, you will likely type more.
使用 dirname + file name 稍微快一点，因为 PHP 不会遍历include_path搜索文件。如果速度很重要，您可能会输入更多。
回答by gaborous
An added note about include('./file.php').
关于 include('./file.php') 的附加说明。
If only speed matters, then yes you can use include('./file.php'), but if you want to resolve dependencies and relative paths issues, you're better off using dirname(__ FILE __), because
如果只是速度很重要，那么是的，您可以使用 include('./file.php')，但是如果您想解决依赖项和相对路径问题，最好使用 dirname(__ FILE __)，因为
include('./file.php')
will still construct paths relative to the executing script (the includingscript), while
仍然会构建相对于执行脚本（包括脚本）的路径，而
include(dirname(__FILE__).'/file.php');
will resolve paths relative to the current script where this line resides (the includedscript).
将解析相对于该行所在的当前脚本（包含的脚本）的路径。
Generally, you're better off using dirname(__ FILE __ ), since './' only gives a negligible performance increase while dirname(__ FILE __ ) gives you a lot more reliable include.
通常，您最好使用 dirname(__ FILE __ )，因为 './' 只会带来微不足道的性能提升，而 dirname(__ FILE __ ) 为您提供了更可靠的包含。
/EDIT: Also note that the benchmark done above only concerns include('./something.php'), which indeed is faster than include('something.php')because you don't have the include_path walking, but when you use dirname(__FILE__)you get the dirname()function call overhead, which makes it slower than walking the include_path (unless you have a lot paths in your include_path).
/编辑：另请注意，上面完成的基准测试只涉及include('./something.php')，这确实比include('something.php')因为您没有 include_path 行走要快，但是当您使用时，您dirname(__FILE__)会得到dirname()函数调用开销，这使得它比行走 include_path 慢（除非您您的 include_path 中有很多路径）。
