What's better of require(dirname(__FILE__).'/'.'myParent.php') than just require('myParent.php')?

user_49318 0
Viewed 31178

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.

Aren't they the same thing? Why do you prefer typing more?

Thanks.

require include php
4 Answers

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_path to get an absolute path and find the file. A better choice would be './myParent.php':

However, it is more efficient to explicitly use include './file' than having PHP always check the current directory for every include.

Gumbo_531140

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.

* Benchmark of include using a path that requires include_path lookup versus a relative path that does not. Tested over 100000 iterations each

Results

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.

Test code

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)

user_1265620

Using dirname + file name is slightly faster, because PHP will not iterate through include_path searching for the file. If speed matters, you will likely type more.

user_2642900
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