PHP Constructor & Destructor Questions

Question

I've been trying to learn the object oriented side of PHP, and was wondering:

If I used a _constructor to open a connection to a database, used a function within that class (eg. insert), would the defined __destructor close the connection after the method "insert" is executed?

class data(){
  function __constructor {
    // connect to db
  }

  function insert($data){
    // mysql_query(...)
  }

  function __destructor {
    // close connection to db
  }
}

$obj = new db();
$obj->insert('mumbo jumbo');

Or would the connection to the database still be open? Cause I read that the destructor is only run if the object is destroyed. But how do you destroy an object?

I think you mean $obj = new data(), not db() since you called your class data. You mention persistent connections --What mysql connection method are you using? I think mysql_pconnect() is the only way to instantiate a persistent connection with mysql. — Mike B
– Mike B, Commented Aug 19, 2009 at 18:36
don't take my code above too seriously, I was merely trying to get my point across. My main question above was to achieve a secure connection by opening and closing the connection to the DB when necessary, as some how increase the security & performance of the website... — chutsu
– chutsu, Commented Aug 19, 2009 at 21:41

Mark · Accepted Answer · 2009-08-19 18:10:42Z

6

In PHP, an object is destroyed when it goes out of scope. This is normally when the script stops executing or when the function it was created within ends, but you can destroy an object early in your code using:

unset($my_variable);

So, to answer your question, you should be fine allowing the destructor to handle closing the DB for you in most situations, especially with small scripts.

answered Aug 19, 2009 at 18:10

Mark

2,0711 gold badge16 silver badges17 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

chaos Over a year ago

Note that that line will only result in the object being deallocated and its destructor being called if $my_variable is the last thing pointing to the object.

chaos · Accepted Answer · 2009-08-19 18:12:21Z

3

Yes, that will work fine, as long as you use the correct names, __construct() and __destruct(), for your constructors and destructors, as opposed to what you have there.

answered Aug 19, 2009 at 18:12

chaos

125k34 gold badges306 silver badges310 bronze badges

Comments

Ferdinand Beyer · Accepted Answer · 2009-08-19 18:12:33Z

2

The object is destroyed once there is no more reference to it, for example by unset()-ting the last variable holding the object or when the script execution terminates.

By the way, the magic methods are named __construct and __destruct, without the trailing -or.

answered Aug 19, 2009 at 18:12

Ferdinand Beyer

67.6k18 gold badges160 silver badges147 bronze badges

Comments

Paul Biggar · Accepted Answer · 2009-08-19 18:13:54Z

1

BTW, the constructors and destructors are called __construct and __destruct.

__destructor would be called when there are no more references to the the db. Typically, this occurs when the object goes out of scope, but if you have saved other references to it, this won't happen. You can remove references to the db using

unset($obj);

and likewise if you have stored $obj anywhere.

answered Aug 19, 2009 at 18:13

Paul Biggar

29k26 gold badges105 silver badges156 bronze badges

Comments

Anti Veeranna · Accepted Answer · 2009-08-19 18:20:24Z

0

Keep in mind that PHP also supports persistent connections to databases, which means that even if your object has been destroyed, the connection to DB is still open "in the background" and will be reused when you call the correspondending pconnect (or PDO analogue) the next time.

answered Aug 19, 2009 at 18:20

Anti Veeranna

11.6k4 gold badges45 silver badges63 bronze badges

2 Comments

Mike B Over a year ago

To clarify, PHP supports persistent connections if you use mysql_pconnect() which is, generally-speaking, frowned upon. All the other mysql connect methods, AFAIK, automatically close when the script has finished executing.

Anti Veeranna Over a year ago

Oh there are others besides mysql_pconnect, like pg_pconnect, sybase_pconnect, etc The are better ways in the world to do connection pooling, you are absolutely right about that. I just thought that this is a appropriate place to mention it, since the question was about 'closing database connection'.

Collectives™ on Stack Overflow

PHP Constructor & Destructor Questions

5 Answers 5

1 Comment

Comments

Comments

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

1 Comment

Comments

Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related