Code Clinic: PHP
Illustration by Don Barnett

Code Clinic: PHP

with David Powers

Video: Setting up the database

Before diving into the PHP side of this project, let's take a And it contains two tables.
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  1. 8m 49s
    1. Welcome
      1m 18s
    2. What you should know before watching this course
      4m 40s
    3. Using the exercise files
      1m 56s
    4. Getting the most from Code Clinic
  2. 1h 34m
    1. Introducing Lake Pend Oreille
      5m 4s
    2. Overview of my solution
      3m 22s
    3. Setting up the database
      4m 55s
    4. Retrieving the full-year records
      5m 20s
    5. Processing the full-year records
      10m 49s
    6. Priming the date_recorded column
      7m 47s
    7. Inserting the full-year data into the database
      6m 48s
    8. Processing individual days
      6m 54s
    9. Retrieving a year's data a day at a time
      7m 41s
    10. Keeping the data up to date
      4m 27s
    11. Calculating the mean and median values
      7m 21s
    12. Creating a web service
      6m 21s
    13. Getting the required data
      6m 50s
    14. Building the web service response
      10m 38s
  3. 49m 47s
    1. Identify the image subset
      3m 14s
    2. Overview of my solution
      3m 19s
    3. Setting up the files
      2m 43s
    4. Calculating the scaling ratio
      6m 28s
    5. Using a custom class to scale images
      6m 25s
    6. Generating the thumbnails
      7m 49s
    7. Using subimage-search in ImageMagick
      4m 32s
    8. Analyzing the image statistics
      4m 45s
    9. Finding the cropped images
      7m 13s
    10. Running the script and displaying the results
      3m 19s
  4. 39m 3s
    1. A classic CS interview question
      2m 4s
    2. Overview of my solution
      3m 48s
    3. Finding all possible combinations
      6m 26s
    4. Detecting horizontal attacks programmatically
      4m 8s
    5. Implementing the checkLayout() function
      6m 25s
    6. Rotating the chessboard
      4m 59s
    7. Eliminating duplicate solutions
      6m 34s
    8. Displaying the unique solutions
      4m 39s
  5. 21m 33s
    1. Build a musical instrument using mouse movements
      1m 35s
    2. Overview of my solution
      2m 1s
    3. Using the Web Audio API
      2m 47s
    4. Creating the tone generator
      7m 39s
    5. Controlling the frequency and volume
      7m 31s
  6. 31m 29s
    1. Searching directories for photos
      2m 44s
    2. Overview of my solution
      3m 24s
    3. Finding the images
      5m 30s
    4. Extracting Exif and IPTC metadata
      6m 18s
    5. Extracting XMP metadata
      6m 22s
    6. Reorganizing the folder structure
      7m 11s
  7. 39m 41s
    1. Building the web NEW
      1m 47s
    2. Overview of my solution NEW
      1m 50s
    3. Getting data from a CSV file: The basics NEW
      4m 29s
    4. Automatically generating an HTML table from a CSV file NEW
      7m 48s
    5. Displaying the table in a webpage NEW
      6m 26s
    6. Creating an associative array from a CSV file NEW
      3m 55s
    7. Displaying the array elements in a webpage NEW
      6m 30s
    8. Dealing with different CSV formats NEW
      6m 56s

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Watch the Online Video Course Code Clinic: PHP
4h 44m Intermediate Jul 15, 2014 Updated Dec 16, 2014

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Many successful programmers know more than just a computer language. They also know how to think about solving problems. They use "computational thinking": breaking a problem down into segments that lend themselves to technical solutions. Code Clinic is a series of six courses where authors solve the same problems using different programming languages. Here, David Powers works with PHP.

Each month, David will introduce a new challenge and provide an overview of his solution in PHP, explaining how he broke the problem up into logical components, and revealing the difficulties he encountered. Challenges will include topics such as statistical analysis, searching directories for images, and accessing peripheral devices.

Visit other courses in the series to see how to solve the exact same challenge in languages like C#, C++, Java, Python, and Ruby. And check back every month for new challenges.

David Powers

Setting up the database

Before diving into the PHP side of this project, let's take a look at how the raw data will be stored in a database. I'm using MySQL and phpMyAdmin, but you can use the database of your choice. Instead of going through the database setup step by step, I'll focus on the decisions I made and why. By the way, if you need help with creating database tables and user accounts in MySQL, take a look a my course, Up and Running with phpMyAdmin in the online training library.

I decided to create a separate database called pendoreille. So let's take a look at that by clicking the pendoreille link on the left here. And it contains two tables. The first table, environmental data, contains the measurements from 2001 to early 2014. The second one, serialized data, only goes up to May 2010 and if I zoom in a little and if we look at the size over here on the right hand side, you can see why I abandoned the serialized data table.

Although it contains less data, it's nearly four times the size of the other table. It's 58.5 megabytes, as opposed to 17 and a half megabytes. So, how did I manage to cram a lot more data into a much smaller space. Well, let's first take a look at the structure of the serialized_data table. It contains four columns. The first one, date_recorded, is a date data type and the other three are all blobs, binary large objects.

I chose blob as the data type because my first instinct had been to gather the data into arrays. And to use the PHP serialize function to store them in the database. Serialized data needs to be stored as a blob. When retrieving the data from the database I used unserialized to convert them back into arrays. And that worked very well, but it bloated the database far too much. After all, the text files that contain all of the historical data up to May 2010 are only half the size, about 29 megabytes.

It's not the data type that caused the bloat but the extra information that's stored with a serialized array. So, let's take a look at the other table, environmental data. This also contains four columns. The first one, data recorded, is data data type. The other three are text data types. So, this table uses text, rather than blob. And if we browse the contents of the table. And then scroll down. You can see that the raw data is stored as comma-separated strings.

All of the white space has been stripped out to make the data as compact as possible. And with some dates, the value is null because there was no data available for that particular date. So, let's just go over the table structure again. Date recorded uses the date data type and it's the table's primary key but it's not auto indexed. The air_temp, bar_press and wind_speed are all text data types and the default value is null because some dates don't have any records.

You don't need the serialized data table, I've got that purely here to show you the comparative size. I also set up two user accounts for the pendoreille database. So, let's just take a look at the user accounts, go to Users, and here are the two accounts, there's pend admin and pend user. Pend Admin is used to insert and update the data, so has all privileges. Pend User will be used for the web service, so it's restricted to the select privilege. That will avoid the danger of data being corrupted by a malicious attacker.

If you want to replicate this setup in your own MySQL database, you can use pendoreille.sql in the Exercise Files for this video. Just load the homepage of phpMyAdmin, then click the Import tab at the top center, and then choose File. You'll need to select pendoreille.sql, and then, when you've selected that, go down to the bottom and click Go. That will create the database called pendoreille, set up the structure of the environmental data table, and create the two user accounts with the ultra secret password lynda all in lower case.

When you got the database organized, the next step is to gather the historical data from the pendoreille website

Find answers to the most frequently asked questions about Code Clinic: PHP .

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Q: I'm encountering script errors message with the prime_dates.php file used in the "Priming the date_record column" movie in this course. How can I resolve these errors?
A: To avoid script errors, use bindValue() instead of bindParam() in Line 9 of the prime_dates.php file. You can also download the latest copy of the exercise files, which corrects this issue for you. For a more in-depth explanation of the difference between bindValue() and bindParam(), check out the "Binding input and output values" video ( in Accessing Databases with Object-Oriented PHP.

Q: Why can't I access the Lake Pend Orielle site (

A: The Lake Pend Orielle site is not accessible in some geographical areas. We have contacted the owner of the server to try to resolve this issue.

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