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Problem with working directory in destructor in php

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Release: 2016-07-25 09:07:27
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  1. class Test {
  2. public function __construct(){
  3. $this->_log('start');
  4. }
  5. public function __destruct () {
  6. $this-> _log('finish');
  7. }
  8. public function _log ($str) {
  9. error_log($str . "n", 3, './log.log');
  10. }
  11. }
  12. $test = new Test;
  13. ?>
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and found that there is only start in log.log and no finish.

After clearing the contents in the log, modify the program: unset($test); Sure enough, there was a start and a finish.

It seems that __destruct will be executed only after unset.

But the matter is not over yet. I modified the program again, changed the __destruct function, and deleted the unset code:

  1. public function __destruct () {
  2. echo 'finish';
  3. $this->_log('finish');
  4. }
  5. ?>
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At this time, 'finish' was actually printed on the screen, which proved that the destructor was indeed executed.

After being puzzled, I started looking for information on the Internet and saw that error_log was used in the destructor of a friend and was executed. The difference from my usage is that he did not specify the error_log file, but set it to the default log file, so I simulated it and modified my program:

  1. public function _log ($str) {
  2. error_log($str . "n");
  3. error_log($str . "n", 3, './log.log') ;
  4. }
  5. ?>
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I found that the log.log still started after start, but there was no finish. And E:AppServApache2.2logserror.log (the default log file of my apache configuration) really has start and finish. It was a strange question and I couldn’t figure it out, so I went to the group to ask. My friends in the group either asked me to check for syntax errors or to check file permissions. I made sure there were no problems with these two. I said, "There is no permission problem in the Windows system. It is definitely not caused by this." A group friend said: "windos system, no explanation!" I said: "This must have nothing to do with the system. I suspect it is an apache problem." So I restored the _log and ran it on the linux+nginx virtual machine.

  1. public function _log ($str) {
  2. error_log($str . "n", 3, './log.log');
  3. }
  4. ?>
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log.log and start and finish are successfully written.

This makes me doubt my judgment even more: it’s caused by apache

So I struggled for an hour, installed apache on the server and ran the file. Still the same result, finish was not successfully written.

At this time, a colleague told me, try writing an absolute path, so I modified another _log

  1. public function _log ($str) {
  2. error_log($str . "n", 3, '/var/www/apache/log.log');
  3. }
  4. ?> ;
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Look at it again and write "finish" successfully. I'm so excited. I finally found the problem. I modified the program again.

  1. public function __construct(){
  2. echo getcwd(). ;br />';
  3. }
  4. ?>
  5. Copy the code
to view the running results: /var/www/apache / Run it under the nginx server and get the result: /var/www/apache /var/www/apache

It turns out that the destructor of apache will change the directory of the current program, so if you use a relative directory, the corresponding file will not be found, and the writing will of course fail. Learning a language is not easy, it pays to practice more.

source:php.cn
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