LISTSERV mailing list manager LISTSERV 16.5

Help for CODE4LIB Archives


CODE4LIB Archives

CODE4LIB Archives


CODE4LIB@LISTS.CLIR.ORG


View:

Message:

[

First

|

Previous

|

Next

|

Last

]

By Topic:

[

First

|

Previous

|

Next

|

Last

]

By Author:

[

First

|

Previous

|

Next

|

Last

]

Font:

Proportional Font

LISTSERV Archives

LISTSERV Archives

CODE4LIB Home

CODE4LIB Home

CODE4LIB  April 2015

CODE4LIB April 2015

Subject:

Re: replacing deprecated PHP code throughout website

From:

Will Martin <[log in to unmask]>

Reply-To:

Code for Libraries <[log in to unmask]>

Date:

Wed, 29 Apr 2015 12:50:41 -0500

Content-Type:

text/plain

Parts/Attachments:

Parts/Attachments

text/plain (112 lines)

> 1.       Is there a general consensus on what the best long-term
> alternative to the mysql_* functions is?

It's my impression that PDO is basically the way to go.

> 2.       Does anyone have advice about how to proceed with an enormous
> overhaul like this?

Define the scope of your project clearly at the beginning.  If all you 
want to do is replace mysql_* with PDO functions, then do that and don't 
let yourself get sidetracked with other bits of refactoring.  Make a 
note of other things that need revisiting, and visit them AFTER you've 
finished with your database functions.

On the other hand, you might decide that you want to do more than just a 
1:1 function replacement.  For example, you might want to write a small 
library of database functions that wrap around PDO (or whatever), and 
then refactor the rest of your code to use THOSE, so that the next time 
this happens you can just rewrite your library of database functions and 
everything else should keep working untouched.  This is getting into the 
territory of writing your own database abstraction layer, though, which 
can be involved.

Regardless, sit down and plan out what you're going to do in detail.  
The more time spent on planning, the less likely it is that you'll 
overlook something and wind up having to backtrack and redo stuff you 
just did.

Besides that, may I suggest using something like grep to generate a list 
of places you need to visit?  Something like issuing the following 
command at the top of your working directory:

     grep -r mysql_ *.php > ~/msqyl-functions

... will walk through the entire directory tree, examine the contents of 
every file, and identify every line containing "mysql_", which is very 
helpful for not missing things.

> 3.       I wonder what other broad-sweeping old-fashionednesses may
> also be about to rear up and bite me. If you imagine that I learned
> procedural (almost never object-oriented) PHP 4 in about 2000 and am
> slow to change my ways, can you predict what sort of deprecated
> foolishness I might still be perpetrating?

I learned about the same time, but I switched to PDO some time ago.  Are 
you familiar with using bound parameters?  If not, you should get 
familiar.  They make it a lot harder for potential attackers to inject 
hostile SQL into your code.

On the other hand, they also make it somewhat more difficult to debug 
your SQL.  When you're not using bound parameters, you might have some 
code like this:

$last_name = mysql_real_escape_string($last_name);

$SQL = "SELECT * FROM students WHERE lname = '".$last_name."'";

$result = mysql_query($SQL, $DB);

This is fairly straightforward.  You build the SQL query, and you send 
it to the database, then read back the result.  If something goes wrong, 
you have the exact SQL as it was executed against the database.  In the 
event that you're not getting sufficient information about what's going 
wrong from mysql_error(), you can always assemble the SQL manually and 
execute it yourself, without involving PHP at all.

That's more difficult with bound parameters.  Those might look something 
like:

$SQL = "SELECT * FROM students WHERE lname = :name";

$query = $DB->prepare($SQL);

$query->execute(array(
     ":name" => $last_name,
));

$result = $query->fetchAll();

In this code, which is not much longer than the original, PHP is 
actually building and executing three separate SQL commands:

PREPARE studentSQL FROM 'SELECT * FROM users WHERE lname = ?';
SET @a = "O\'Grady";
EXECUTE studentSQL USING @a;

First it prepares the SQL, without any of the actual data that you feed 
in as a limiter.  Then, the data is bound to a variable name within 
MySQL.  Finally, the prepared statement is executed, with the variables 
plugged in.  Oh, and there's a cleanup phase afterwards which unsets the 
statement and the variables, I believe.

Because the data is bound to a variable name separate from the SQL 
statement, it is effectively impossible to mix hostile content into the 
query.  MySQL knows that everything in that variable is data, not SQL, 
and should be treated as data pure and simple.  So it's great for 
eliminating SQL injections.

But it does make it a little harder to debug, because it's a bit harder 
to see exactly what is getting sent to MySQL.  I've sometimes set up 
query logging on my dev box just to track down EXACTLY what is getting 
sent to the server, or else gone to the trouble of manually setting up 
and executing prepared statements to test them.

Hope this is helpful.


Will Martin

Web Services Librarian
Chester Fritz Library
University of North Dakota

Top of Message | Previous Page | Permalink

Advanced Options


Options

Log In

Log In

Get Password

Get Password


Search Archives

Search Archives


Subscribe or Unsubscribe

Subscribe or Unsubscribe


Archives

February 2020
January 2020
December 2019
November 2019
October 2019
September 2019
August 2019
July 2019
June 2019
May 2019
April 2019
March 2019
February 2019
January 2019
December 2018
November 2018
October 2018
September 2018
August 2018
July 2018
June 2018
May 2018
April 2018
March 2018
February 2018
January 2018
December 2017
November 2017
October 2017
September 2017
August 2017
July 2017
June 2017
May 2017
April 2017
March 2017
February 2017
January 2017
December 2016
November 2016
October 2016
September 2016
August 2016
July 2016
June 2016
May 2016
April 2016
March 2016
February 2016
January 2016
December 2015
November 2015
October 2015
September 2015
August 2015
July 2015
June 2015
May 2015
April 2015
March 2015
February 2015
January 2015
December 2014
November 2014
October 2014
September 2014
August 2014
July 2014
June 2014
May 2014
April 2014
March 2014
February 2014
January 2014
December 2013
November 2013
October 2013
September 2013
August 2013
July 2013
June 2013
May 2013
April 2013
March 2013
February 2013
January 2013
December 2012
November 2012
October 2012
September 2012
August 2012
July 2012
June 2012
May 2012
April 2012
March 2012
February 2012
January 2012
December 2011
November 2011
October 2011
September 2011
August 2011
July 2011
June 2011
May 2011
April 2011
March 2011
February 2011
January 2011
December 2010
November 2010
October 2010
September 2010
August 2010
July 2010
June 2010
May 2010
April 2010
March 2010
February 2010
January 2010
December 2009
November 2009
October 2009
September 2009
August 2009
July 2009
June 2009
May 2009
April 2009
March 2009
February 2009
January 2009
December 2008
November 2008
October 2008
September 2008
August 2008
July 2008
June 2008
May 2008
April 2008
March 2008
February 2008
January 2008
December 2007
November 2007
October 2007
September 2007
August 2007
July 2007
June 2007
May 2007
April 2007
March 2007
February 2007
January 2007
December 2006
November 2006
October 2006
September 2006
August 2006
July 2006
June 2006
May 2006
April 2006
March 2006
February 2006
January 2006
December 2005
November 2005
October 2005
September 2005
August 2005
July 2005
June 2005
May 2005
April 2005
March 2005
February 2005
January 2005
December 2004
November 2004
October 2004
September 2004
August 2004
July 2004
June 2004
May 2004
April 2004
March 2004
February 2004
January 2004
December 2003
November 2003

ATOM RSS1 RSS2



LISTS.CLIR.ORG

CataList Email List Search Powered by the LISTSERV Email List Manager