PHP require/include differences

Preface

stay PHP in , Loading files can optionally use require, You can also use include, So what's the difference between them ? Read some articles on the Internet , Say they use different scenarios , require Generally, the file is introduced at the beginning of the file , include Generally, files are dynamically introduced into functions .

But I don't think it's that simple , require Is as a language structure ( keyword ) The emergence of , Keywords are generally the less the better for language designers , Keywords are simple without language . So I decided to go deep into the source code level to improve their differences .

To explore the

By looking at , require/require_once/include/include_once These methods are the same after translation c function ZEND_INCLUDE_OR_EVAL_SPEC_CONST_HANDLER.

How to get this c Functions can be found in this article : https://hujingnb.com/archives/836

Check the method :

include/require

include/require Methods are handled in the same way . Let's look at their differences first , Let's see _once Differences in methods .

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By looking for , include And require The only difference , When the file does not exist, the processing method is different .

Search again , The processing method for both is shown in the figure ( This error report is indeed a copy when the document does not exist ). The functions of the two methods called are as follows :

• php_error_docref: Throw out php Level error . Because what is thrown here warning Level , It will not stop the script .
• zend_throw_error: Throw a compile time exception , Will terminate the script execution .

therefore , Through comparison, we can see , require and include The only difference , When the file does not exist , require Will terminate the script execution , include Throw only warning error .

Here it is zend_throw_error The following comments are seen in the method , It mentions that compile time errors cannot currently be converted to exception. May support in the future ??

include_once/require_once

By looking at the source code , include_once/require_once The difference between , And include/require equally , They are different in handling exceptions , The others are exactly the same

Conclusion

therefore , include and require The only difference , When the file does not exist , require Will terminate the process , and include Can't .

ah , this , It's really good to have two similar keywords , if , take require Get rid of , And then through include Return value to determine whether the file exists , It is up to the caller to decide whether to terminate the process , Would this be more reasonable ? Also, or PHP Our designers are motivated by other considerations ?

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