PHP各种读取文件的函数效率对比[Readfile vs include]

It is not often that you can write a PHP script that does not need to include the contents of different files as part of it's output. If these includes happen to be php scripts themselves you have no choice but to use require or include. However more often than not, the contents are static, usually html template component. With static includes you have many more options available. aerwear We will analyse some of these functions to find out which one is most suitable when dealing with files with static content. We use the term function loosely, because require and include are not real functions but language constructs.

Function	Brief Description
string file_get_contents ( string filename [, int use_include_path])	Reads entire file into a string
int fpassthru ( resource handle)	Output all remaining data on a file pointer
string fgets ( resource handle [, int length])	Gets line from file pointer
array file ( string filename [, int use_include_path])	Reads entire file into an array
require(string filename) include(string filename) require_once(string filename) include_once(string filename)	includes and evaluates the specific file.
int readfile ( string filename [, int use_include_path])	Outputs a file

We will now attempt to 'include' the contents of a 1 megabyte file into the output produced by our php script. How you can generate files of specific sizes is described . The execution times and peak memory consumption, as reported by xdebug have been tabulated below.

We compensate for file caching and background processes by executing each script 4 times and taking the average (mean) of the result number 2-4. The first result is always rejected. Any result that appears to be outlier is rejected. The mean is rounded to 5 decimal places.

Function	Sample Usage	Time (s)	Memory (b)
file_get_contents	echo file_get_contents($filename);	0.00564	1067856
fpassthru	fpassthru($fp);	0.00184	20032
fgets	$fp = fopen($filename,"rb"); while(!feof($fp)) { echo fgets($fp); }	0.07190	30768
file	echo join("",file($filename));	0.06464	2185624
require_once	require_once($filename);	0.08065	2067696
include	include($filename);	0.08202	2067696
readfile	readfile($filename);	0.00191	19208

What's obvious from these results is that using fpassthru is far superior to all other methods. What's not so obvious is that fpassthru and readfile are equally good. The fpassthru version runs 0.00007 seconds quicker than the readfile version. What that really means is that you need to run the script at least 100000 times to make significant saving. On memory consumption readfile seems to have use up around 1kb less than passthru. A kilo byte is a drop in the ocean for modern web servers with hundreds of megabytes if not gigabytes of memory.

The only conclusion that can be drawn from these studies is that fpassthru and readfile are equally good if you wish to include static content as part of the script's output.

Before you rush off to change all your includes and requires into readfiles or fpassthrus let's run the same test with a smaller (32Kb file). 32Kb is a more realistic size for an included file.

Function	Time (s)		Memory (b)
	32Kb File	1Mb File	32Kb File	1Mb File
file_get_contents	0.00152	0.00564	52480	1067856
fpassthru	0.00117	0.00184	20016	20032
fgets	0.00195	0.07190	30760	30768
file	0.00157	0.06464	87344	2185624
require_once	0.00225	0.08065	67992	2067696
include	0.00222	0.08202	67928	2067624
readfile	0.00117	0.00191	19192	19208

readfile and fpassthru have once again tied for first place. This new set of results just confirms the fact that speed and scalability comes from your design and not from your code. The difference between the best performance and the worst is just 0.00108s too close to call.

The most significant feature of these results is that both fpassthru and readfile scale really well. In other words, memory consumption and execution time does not increase significantly with increase in file size. That does not always mean your script will be faster just because you use these functions instead of require or include.

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