Professional Refactoring
International PHP Conference 2009
Spring Edition
Mayflower GmbH 2009 1

• Senior Developer / Team Lead at
Mayflower GmbH
• Reporting and Rating Apps
• QA and PHP 5 Migration
consultings
• PHP since 1999 (3.0.16)
• phpMyFAQ since 2001
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Who are you?
• What are you doing?
• What‘s your team size?
• Using MVC?
• Who‘s using Continous Integration?
• PHPUnit?
• 80% code coverage?
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Your projects...
• What‘s your average project lifetime?
• Is there PHP code more than 5 years old?
• How many lines of code?
• How many change requests per year?
• Has there been a specification?
• Were all features in the first
release as specified?
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What is Refactoring?
„Refactoring is a disciplined technique for
restructuring an existing body of code, altering
its internal structure without changing its
external behavior.“
-Martin Fowler, www.refactoring.com
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Why especially PHP?
(c) www.medrehab.com
Code Aging!
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A PHP Project in 2000 ...
• no coding standards, no PHPDoc
• no MVC, no Design Patterns
• if you were lucky, someone used a
template system
• nobody cared about XSS or CSRF
a lot of changes in business logics
• never got refactored,
documentated or even tested ...
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... because it worked!
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In the year 2009
• change requests get more and
more expensive
• the bug rate is always
increasing
• the development team
motivation is decreasing
• requirement changes are
almost impossible
• new team members need a lot
of time to be productive
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Management point of view
Costs per Change Request
rising frequency
Dead end!
Benefit per Change Request
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Start refactoring now!
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But hey, stop!
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Don‘t refactor ...
• weeks before a
important release
• only with a lot of junior
developers
• parallel with
development tasks
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Before starting refactoring
• define a coding standard
• avoids spaghetti code
• speeds up maintainability
• improves productivity
• fix your API specs
• complete your documentation
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During the refactoring...
• stay calm
• take a lot of good developers and
a bunch of juniors
• write tests, tests, tests
• don‘t let developer refactor their
own code
• don‘t let junior developers
refactor alone
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About Unittests
• Testing is essential during refactoring
• Problems
• most of old code isn‘t
„unittestable“
• API breaks during refacotoring
• Solution
• Selenium tests instead
• iterative refactoring
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(c) BMW AG
Okay, let‘s start!
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Back to Martin Fowler
„Refactoring is a disciplined technique for
restructuring an existing body of code, altering
its internal structure without changing its
external behavior.“
-Martin Fowler, www.refactoring.com
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Forms of refactoring
•Renaming
•Extraction
•Changing signature
•Pull up / Pull down
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Renaming
/**
* Remove a word from the stop word dictionary
*
* @param integer $id
*
* @return void
*/
public function remove($id)
{
$sql = sprintf(\"DELETE FROM $this->tablename WHERE id = %d AND lang =
'%s'\", $id, $this->language);
$this->db->query($sql);
}
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Renaming
/**
* Remove a word from the stop word dictionary
*
* @param integer $stopword_id ID of the stop word
*
* @return void
*/
public function remove($stopword_id)
{
$delete = sprintf(\"DELETE FROM $this->tablename WHERE id = %d AND lang =
'%s'\", $stopword_id, $this->language);
$this->db->query($delete);
}
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Restructuring
/**
* Remove a word from the stop word dictionary
*
* @param integer $stopword_id ID of the stop word
*
* @return void
*/
public function remove($stopword_id)
{
$delete = sprintf(\"DELETE FROM $this->tablename WHERE id = %d AND lang =
'%s'\", $stopword_id, $this->language);
$this->db->query($delete);
}
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Restructuring
/**
* Remove a word from the stop word dictionary
*
* @param integer $stopword_id ID of the stop word
*
* @return void
*/
public function remove($stopword_id)
{
$delete = sprintf(\"DELETE FROM %s WHERE id = %d AND lang = '%s'\",
$this->tablename,
$stopword_id,
$this->language);
$this->db->query($delete);
}
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Extraction
/**
* Remove a word from the stop word dictionary
*
* @param integer $stopword_id ID of the stop word
*
* @return void
*/
public function remove($stopword_id)
{
$delete = sprintf(\"DELETE FROM %s WHERE id = %d AND lang = '%s'\",
$this->tablename,
$stopword_id,
$this->language);
$this->db->query($delete);
}
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Extraction
public function remove($stopword_id)
{
$delete = sprintf(\"DELETE FROM %s WHERE id = %d AND lang = '%s'\",
$this->tablename,
$stopword_id,
$this->language);
$this->_execute($delete);
}
private function _execute($query)
{
return $this->db->query($query)
}
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Changing signature
/**
* Remove a word from the stop word dictionary
*
* @param integer $id ID of the stop word
*
* @return void
*/
public function remove($stopword_id)
{
$delete = sprintf(\"DELETE FROM %s WHERE id = %d AND lang = '%s'\",
$this->tablename,
$stopword_id,
$this->language);
$this->db->query($delete);
}
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Changing signature
/**
* Remove a word from the stop word dictionary
*
* @param integer $stopword_id ID of the stop word
* @param boolean $logging Log removal? Default: false
*
* @return void
*/
public function remove($stopword_id, $logging = false)
{
$delete = sprintf(\"DELETE FROM %s WHERE id = %d AND lang = '%s'\",
$this->tablename,
$stopword_id,
$this->language);
if ($logging) {
$this->_logAction('removal', $stopword_id);
}
$this->db->query($delete);
}
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Pull up / Pull down
x
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Pull up / Pull down
x
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Pull up / Pull down
x
x x
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Tips & Tricks
• Always add PHPDoc if it‘s missing
• Never trust automatic refactoring of IDEs
• Don‘t do refactoring for fun
• Write as much unittests as possible
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Any questions? Mayflower GmbH 2009 32

Thank you very much for your attention!
Thorsten Rinne
Mayflower GmbH
Mannhardtstraße 6
D-80538 München
+49 (0) 89 24 20 54 - 31
thorsten.rinne@mayflower.de
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