TweetFollow Us on Twitter

Mac in the Shell: Data Manipulation with PHP

Volume Number: 24 (2008)
Issue Number: 04
Column Tag: Mac in the Shell

Mac in the Shell: Data Manipulation with PHP

PHP provides easy access to MySQL on OS X

by Edward Marczak

Introduction

Last month, we covered some of the basics of scripting with PHP. This month, we'll continue and talk about database access and string manipulation with PHP. Thanks to a pretty full install of PHP as the default in OS X, we don't have to worry about fetching, configuring, compiling and installing PHP - we can just get on with writing our script.

Working Environment

Last month, I mentioned that there are plenty of OS X-based editors that 'understand' PHP. This comes in the form of syntax coloring, appropriate code snippets, code completion and auto indentation. Before we continue, there are two more things that I should mention.

Coda, from Panic Software, is one of those editors - one that I should have mentioned last month. It's actually quite a bit more than a simple text editor: It's a full web development environment. I really mention it here because it has a way to access PHP documentation built right in (along with HTML, Javascript and more). Since PHP is such a popular web development language, as a web development tool, this made sense. At last check, though, access to this documentation was only available while you have an Internet connection.

I, on the other hand, am very much of an offline person. I want/need to accomplish things while on a plane, train, or wherever I may not have a good signal from some source, for whatever reason. Due to that, I've come to rely on the PHP Function Reference widget for Dashboard. Downloadable from here: http://code.google.com/p/phpfr/ (it has been "open sourced" since its introduction, and now lives as a Google Code project). Weighing in at close to 40MB, it's a little larger than your average widget, but that's the price you pay to carry around the entire PHP function set with descriptions. As a Dashboard widget, it lives out of sight until you need it. With a search function built-in, I tend to reach for this a lot. Highly recommended.

The Setup

I do a lot of data manipulation and migration work, and scripting languages are an essential part of the process. Perl, Ruby and Python are all good contenders for that position, but this particular column is about PHP! Our sample project this month will extract data from a MySQL database and give us a CSV file, ready for importing into another system. "But Ed," you say, "you can do that with MySQL alone!" While this is true, we aren't allowed to manipulate the data too drastically in that process.

Let's imagine that the data in our source system is stored with a single column for full name, but our target system wants separate first name and last name. Or that we need to go gather more data (like a zip+4 based on address) per record. There are hundreds of reasons you may need to filter the data as it goes from the database to a CSV file.

Connecting to the Database

One variable type that I left out of our discussion last month is resource. We looked at string, integer and other built-in types, but 'resource' really warrants its own discussion.

A variable of type "resource" holds a reference to some external resource. This may be a file on disk, a curl session to fetch a URL, a database connection or more. Again, it's just a reference, and you'll need to use functions that know how to access those resources via the resource variable that you pass to them.

First thing that our script needs to do is open a connection to the MySQL server. This happens with the mysql_connect command:

$connection = mysql_connect("server.example.com","user","password");

The mysql_connect command passes back a resource if successful, and FALSE if there's an error. Let's get into good habits right away: check the value of $connection for FALSE. Thankfully, we have access to the error that the server passes back to us in the form of two functions: mysql_errno() and mysql_error(). These functions return the error code from the previous MySQL operation. We should follow our connect, or any database operation with something similar to this:

if (! $connection) {
   print "Connection to database failed with ".mysql_errno()." - ".mysql_error()."\n";
   die();
}

Simply, if $connection is not TRUE (zero, or, FALSE), we print out a message containing the MySQL error information, and then we halt operation of the script and exit with die().

Also, looking at our initial connect string, what's wrong, or at least, what should send shivers up your spine? Yes, a password in a script. Unfortunately, that's just life in the big city, and you'll need to take precautions that allow only the right people to have access to the script. While you can put this information in external files and pull it in, or make your script get it from somewhere, the person that can read your file can also (typically) read how and where to get the password. Here be dragons, so, be conscious of this and plan for protection.

Once connected, we need to specify which database we're going to be working with. That's done with the mysql_select_db() function:

$select = mysql_select_db("customers");
...error checking here ...

All subsequent MySQL functions operate on the selected database. If you're working with more than one server, you can optionally pass in the connection resource that you obtained from mysql_connect():

$conn1=mysql_connect("server1","bob","s3kret");
$conn2=mysql_connect("server2","jane","h1dd3n");
$select1=mysql_select_db("sales",$conn1);
$select2=mysql_select_db("aggregates",$conn2);

...with the proper error checking, of course!

Once those preliminaries are complete, we can now query our database. While you can stuff a query into fewer lines, we're going to split it up in a more conventional manner. The mysql_query() function takes a string as an argument. Assigning the query to a variable makes for easier reading, easier variable substitution, and allows one to build dynamic queries. Let's start with a simple example:

$query="select uid,fname,lname from users";
$result=mysql_query($query);

$query is a simple string, and $result is of type resource. As with our earlier queries, if the execution fails, mysql_query() will return a Boolean FALSE, and our errors can be retrieved with mysql_errno() and mysql_error().

$result is simply a resource, and points to the result set. We now have to use it to fetch the actual data, database row by database row. If you purposefully limited your query to a single row, you could now go fetch it with one line. However, more often than not, you're expecting multiple rows - sometimes thousands. A perfect job for the while loop that we introduced last month:

while ($row=mysql_fetch_assoc($result)) { print "Scanning ".$row['uid'].": ".$row['fname']." ".$row['lname']."\n"; }

That's a lot packed into a small space, so, let's break it down. The data fetching happens with this line:

$row=mysql_fetch_assoc($result)

You could manually call that over and over and get a new row from the database each call. Of course, for large result sets, a loop is the only feasible method. The mysql_fetch_assoc() function returns an associative array. Unlike a "plain" array, you can access values with a key that is a string. In our case, each column from the database becomes an entry in the array. We asked for the fields, "uid", "fname" and "lname", which makes $row become:

$row['uid']
$row['fname']
$row['lname']

..filled with the values from the current row retrieved from the database.

Within the body of the loop, there's a single line: a print statement. It's fairly ugly, though, isn't it? It happens to be pretty standard fare in PHP. The concatenation operator (".") 'glues' two strings together. So, now it should be pretty easy to break down, as we're printing some static text (the bits in quotes) and some dynamic text, filled in by the values in the $row array. Sample output would look like this:

Scanning 1052: Mike Bollinger
Scanning 1053: Laura Wilkinson
Scanning 1055: Joanne Moss
...

Now that we have access to our data, let's get it into a format usable by almost all other apps: CSV.

Data Manipulation

If you simply wanted a CSV file of a MySQL database table, there are many simple ways to do so. However, when moving data from one system to another, we often need to massage the original data into a new format. We get that opportunity in our while loop, where we're accessing each row of the table and before writing it out. PHP has many string manipulation functions to help us do anything our hearts (and brains) desire.

The first thing we may want to do is to simply re-assign a cleaned-up version of a string before writing it out. Consider this:

switch ($row['state']) {
   case "NY":
   case "new york":
   case "noo yrk":
      $state="New York";
      break;
   case "CA":
   case "calif.":
   case "cal":
      $state="California";
      break;
   default:
      $state="Unknown";
}

Rather than writing six separate if statements, I chose to use a single switch statement. This is a) cleaner code and b) a nice introduction to the switch statement, which I did not cover last month. Generally, the switch statement will test a single expression for the results you choose to test for. In the preceding example, we're examining the variable "$row['state']". Each case statement within the switch block acts as an "if" statement, and all code through the following break statement is executed. The code in the default block matches when no other case statements match. While the switch statement may contain virtually any expression, the match in each case statement can only be a simple type: string, integer or floating-point. You cannot evaluate arrays or objects here. For these more complex cases, you still must rely on an if statement.

The simple line doing all of the work here is this: $state="...". We're just assigning a literal to our variable. We're even free to re-assign $row['state'] if it suits our needs and style.

One of the coolest ways to tear up a string is the explode() function. As always, an example is best:

$animal="bear cat dog elephant";
$the_animals=explode(" ",$animal);
After this runs, $the_animals will be an array containing:
$the_animals[0]="bear"
$the_animals[1]="cat"
$the_animals[2]="dog"
$the_animals[3]="elephant"

explode() can split based on any delimiter, not just a space. However, this is extremely useful for splitting up a full name. If you know that all entries in the database are in firstname-space-lastname format, then this will do what you want:

list($fname, $lname) = explode(" ",$fullname);

However, the reason you're probably involved is due to a more complex nature of the data. If most names are in two-name format, but some may contain a middle initial, too, then we have a few options. One would be to toss the middle initial, or include it in the first name. In that scenario we need to test how many elements were returned:

$fullname="William S. Fatire";
$names=explode(" ",$fullname);
if (count($names) > 2) {
   $fname=$names[0]." ".$names[1];
   $lname=$names[2];
} else {
   $fname=$names[0];
   $lname=$names[1];
}
print "The names are:\n";
print "Firstname: $fname\n";
print "Lastname: $lname\n";

The count() function is introduced here and simply returns the number of elements in an array.

Naturally, our target database may have a field for middle initial, in which case, we can retain it and assign it appropriately.

Let's now imagine that we want to create a default user id for our new users. We can base this id on the user's real name. PHP includes some nice string slicing functions. If we want to base the user ID on the user's first initial plus last name, that's simple:

$uid=$fname[0].$lname;

PHP can access string elements by character when you supply the zero-based offset in square brackets. So, in this example, we're just grabbing the first character of $fname.

If you had a more complex uid-creation scheme, it'd be easy to handle, too. If you needed a uid that contained the first three letters from the family name, and the first two from the first name, PHP includes a nice sub-string function. Generically, it looks like this:

substr ($string, $start [,$length ])

This will return a string that starts at '$start' in $string, and runs until the end of the string supplied, or optionally, for $length. Back to our first-three, first-two uid scheme:

$uid=substr($lname,0,3).substr($fname,0,2);

Nice, right? Of course, if you were really implementing this, you'd need to look for duplicates and also check for last names that may be shorter than 3 characters in total (like "Li").

All Together Now

I'd like to put all of this together to create a code snippet that takes data from a database, gives space to manipulate the data, and output a CSV file. Some new elements will also be introduced here.

Listing 1: db2csv.php

01 <?php
02 
03 mysql_connect("127.0.0.1", "dbuser", "dbpass") or
04     die("Could not connect: " . mysql_error());
05 mysql_select_db("mydb");
06 
07 $q="select * from user_profiles order by fid";
08 $r=mysql_query($q);
09 while ($row=mysql_fetch_assoc($r)) {
10    $pf[$row['fid']]=$row['title'];
11 }
12 
13 // Create the header
14 $curcsv="\"uid\",";
15 foreach ($pf as $key=>$val) {
16    $curcsv=$curcsv."\"".$val."\",";
17 }
18 $curcsv=substr($curcsv,0,strlen($curcsv)-1);
19 print "$curcsv\n";
20 
21 $q="select * from users where status=1";
22 $r=mysql_query($q);
23 while ($row=mysql_fetch_assoc($r)) {
24 // Build csv for current user
25    $curcsv="\"".$row['uid']."\",";
26    foreach ($pf as $i=>$val) {
27       $q2="select value from user_profiles where fid=$i and uid=".$row['uid'];
28       $r2=mysql_query($q2);
29       $row2=mysql_fetch_assoc($r2);
30       $curcsv=$curcsv."\"".$row2['value']."\",";
31    }
32    $curcsv=substr($curcsv,0,strlen($curcsv)-1);
33    print "$curcsv\n";
34 }
35 
36 ?>

Newly introduced here is the foreach loop. foreach gives the programmer (you) an easy way to iterate over arrays. Generically, foreach looks like this:

foreach ($array as $value)

The loop interates once for each element of the array, and $value is updated accordingly. A variation to this (seen on line 26 in listing 1) also includes the current key - very useful for associative arrays where the key is text or other representation of the index. That variant is simply:

foreach ($array as $key=>$value)

Breaking down listing 1, lines 1-5 should look familiar: the opening PHP tag, and then try to connect to the database. Line 7 defines the first query to the first table, and line 8 executes that query against the selected database. The while loop starting at line 9 is pretty standard fare, but what's going on in the loop body?

On line 10, we're creating an associative array ($pf) using a variable as the key ("index"). In this case, we're using the result of the database fetch $row['fid']. Pretty slick.

Lines 14 through 17 take case of one small but significant part of writing out a CSV file: making the first line a header that describes the remaining columns. In our case, we can do that with the contents of the array we just created. Another foreach loop neatly solves that. In the body of this loop, we're creating a variable that will hold the current line of the CSV file. Each field is wrapped in quotes, and then followed by a comma.

Line 18 removes the trailing comma from $curcsv, and line 19 prints out $curcsv. Now for the bulk of work.

Lines 21 through 33 handle the main load of this program. Line 21 and 22 set up a new query and execute it. Line 23 brings back our now familiar while loop, fetching one database row at a time. Line 25 starts $curcsv anew each iteration, wrapping the proper value ($row['uid'] in this case) in quotes followed by a comma.

Line 26 gets interesting: we use a new foreach loop to obtain more information about this particular uid for each of the values in $pf - by running a new query. We query and fetch again, and line 30 adds each field retrieved to $curcsv (wrapped and comma'd).

Finally, line 32 takes care of the trailing comma on $curcsv (because we blindly add it after each value), and line 33 prints the row.

Running this, or similar program, will simply dump all output to standard out - we're only using a print statement. You thought we were creating a CSV file? Well, we are! Everything in Unix is a file. Remember our shell redirectors? We can run this program as is and have the chance to visually inspect the output, and, when we're ready, simply redirect to a file:

php db2csv.php > users.csv

This is also a nice euphemism for, "I'm going to cover file manipulation next month!"

Conclusion

I'll continue to say: don't discount PHP as a general scripting language. It's fairly rapid development, has broad capabilities, and will typically be found across platforms (including versions for Windows - but you'll need to install it yourself). As mentioned, I'll cover some more aspects of scripting with PHP next month, including file manipulation.

Media of the month: Inside the Machine: An Illustrated Introduction to Microprocessors and Computer Architecture, by Jon Stokes. It's a very readable introduction to microprocessor architecture, and it's even current enough that it covers up through Intel's Core 2 Duo chips.

Until next time, enjoy your new scripting prowess!

References

Official PHP Documentation: http://www.php.net/docs.php


Ed Marczak is the Executive Editor for MacTech Magazine, and has been lucky enough to have ridden the computing and technology wave from early on. From teletype computing to MVS to Netware to modern OS X, his interest has always been piqued. He has also been fortunate enough to come into contact with some of the best minds in the business. Ed spends his non-compute time with his wife and two daughters.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

Together 3.4.6 - Store and organize all...
Together helps you organize your Mac, giving you the ability to store, edit and preview your files in a single clean, uncluttered interface. Smart storage. With simple drag-and-drop functionality,... Read more
Monosnap 3.1.0 - Versatile screenshot ut...
Monosnap lets you capture screenshots, share files, and record video and .gifs! Capture: Capture full screen, just part of the screen, or a selected window Make your crop area pixel perfect with... Read more
Cocktail 8.5.1 - General maintenance and...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
Vienna 3.0.6 :5eaf312: - RSS and Atom ne...
Vienna is a freeware and Open-Source RSS/Atom newsreader with article storage and management via a SQLite database, written in Objective-C and Cocoa, for the OS X operating system. It provides... Read more
Kodi 15.1.rc1 - Powerful media center to...
Kodi (was XBMC) is an award-winning free and open-source (GPL) software media player and entertainment hub that can be installed on Linux, OS X, Windows, iOS, and Android, featuring a 10-foot user... Read more
Bookends 12.5.8 - Reference management a...
Bookends is a full-featured bibliography/reference and information-management system for students and professionals. Access the power of Bookends directly from Mellel, Nisus Writer Pro, or MS Word (... Read more
Chromium 44.0.2403.125 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 44.0.2403.125: This release contains a number... Read more
iMazing 1.2.2 - Complete iOS device mana...
iMazing (was DiskAid) is the ultimate iOS device manager with capabilities far beyond what iTunes offers. With iMazing and your iOS device (iPhone, iPad, or iPod), you can: Copy music to and from... Read more
Audio Hijack 3.2.0 - Record and enhance...
Audio Hijack (was Audio Hijack Pro) drastically changes the way you use audio on your computer, giving you the freedom to listen to audio when you want and how you want. Record and enhance any audio... Read more
FontExplorer X Pro 5.0.1 - Font manageme...
FontExplorer X Pro is optimized for professional use; it's the solution that gives you the power you need to manage all your fonts. Now you can more easily manage, activate and organize your... Read more

You'll Want to Keep an Eye Out for...
If you're the kind of person who had fun hunting down and completing all the codex puzzles in Assassin's Creed 2, then are you ever in for a treat. The Guides looks like it's going to be a very robust collection of similarily odd, seemingly... | Read more »
Vivid Games has Announced Real Boxing 2...
The original Real Boxing was a pretty impressive bit of fisticuffs, but if the trailer Vivid Games is showing off for GamesCom is any indication Real Boxing 2 is going to be even better. [Read more] | Read more »
PAC-MAN Championship Edition DX - Tips,...
[Read more] | Read more »
Card King: Dragon Wars - Tips, Tricks an...
[Read more] | Read more »
Pac-Man Championship Edition DX has brou...
Bandai Namco has released Pac-Man Championship Edition DX on iOS and Android, which features the classic arcade gameplay that we've all grown to love. Pac-Man Championship Edition DX can be enjoyed in much shorter bursts than the arcade versions... | Read more »
Cosmonautica (Games)
Cosmonautica 1.1 Device: iOS Universal Category: Games Price: $6.99, Version: 1.1 (iTunes) Description: Cast off! Are you ready for some hilarious adventures in outer space? | Read more »
Rescue humanity from a Demon horde in An...
Angel Stone is Fincon's follow up to the massively successful Hello Hero and is out now on iOS and Android. You play as a member of The Resistance, a group of mighty human warriors who have risen up in defiance of the Demon horde threatening to... | Read more »
Gallery Doctor (Photography)
Gallery Doctor 1.0 Device: iOS iPhone Category: Photography Price: $2.99, Version: 1.0 (iTunes) Description: Free up valuable iCloud and iPhone storage with Gallery Doctor, the only iPhone cleaner that automatically identifies the... | Read more »
You Against Me (Games)
You Against Me 1.0 Device: iOS Universal Category: Games Price: $.99, Version: 1.0 (iTunes) Description: A simple game… You. Me. Claim, steal, lock, score, win! | Read more »
Yep, it's True - Angry Birds 2 is O...
The not exactly rumors were true and the birds are back. Angry Birds 2 has come to the App Store and the world will... well I suppose it'll still be the same, but now we have more bird-flinging options! [Read more] | Read more »

Price Scanner via MacPrices.net

PDF Element Tool Kit For PDF For Windows 10,...
South Surrey, British Columbia based software developer Wondershare has posted an interesting infographic tracking the development of Microsoft’s flagship Windows operating system over the years,... Read more
27-inch 3.5GHz 5K iMac on sale for $81 off MS...
Adorama has the 27″ 3.5GHz 5K iMac on sale for $2218, $81 off MSRP, including a free copy of Apple’s 3-Year AppleCare Protection Plan. Shipping is free, and Adorama charges sales tax in NY & NJ... Read more
Back-to-School with Tablet and Smartphone Acc...
Belkin helps you prepare for the coming school year with a wide variety of the latest mobile and tablet accessories to outfit both grade school and college students. The line-up includes charging... Read more
11-inch MacBook Airs on sale for $100 off MSR...
Best Buy has 11-inch MacBook Airs on sale for $100 off MSRP. Choose free shipping or free local store pickup (if available). Sale prices for online orders only, in-store prices may vary: - 11″ 1.6GHz... Read more
iPad Air 2 on sale for up to $100 off MSRP
Best Buy has iPad Air 2s on sale for up to $100 off MSRP on their online store for a limited time. Choose free shipping or free local store pickup (if available). Sale prices available for online... Read more
Sale! 13-inch MacBook Pros on sale for $100 o...
B&H Photo has 13″ MacBook Pros on sale for $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 13″ 2.5GHz/500GB MacBook Pro: $999.99 save $100 - 13″ 2.7GHz/128GB Retina... Read more
Sale! Save $100 on 13-inch MacBook Airs this...
B&H Photo has the 13″ 1.6GHz/128GB MacBook Air on sale for $899.99 including free shipping plus NY tax only. Their price is $100 off MSRP, and it’s the lowest price available for this model.... Read more
Worldwide Tablet Market Decline Continues, Ap...
The worldwide tablet market declined -7.0% year-over-year in the second quarter of 2015 (2Q15) with shipments totaling 44.7 million units according to preliminary data from the International Data... Read more
TP-LINK TL-PA8030P KIT Powerline Featuring Ho...
Consumer and business networking products provider TP-LINK is now shipping its TL-PA8030P KIT AV1200 3-Port Gigabit Passthrough Powerline Starter Kit that expands your home’s network over its... Read more
Apple refurbished iPad Air 2s available for u...
The Apple Store has Apple Certified Refurbished iPad Air 2s available for up to $140 off the price of new models. Apple’s one-year warranty is included with each model, and shipping is free: - 128GB... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Infrastructure Engineer - *Apple* /Mac - Hil...
Infrastructure Engineer - Apple /Mac Job Code: 1608 # of openings: 1 Description Our fortune 500 client is looking to hire an experienced Infrastructure Engineer to join Read more
Executive Administrative Assistant, *Apple*...
…supporting presentation development for senior leadership. * User experience with Apple hardware and software is preferred. Additional Requirements The following list Read more
*Apple* Bus Company is now hirin - Apple Bus...
Apple Bus Company is now hiring school bus drivers in the Pettis County area. Class B CDL preferred. Free training provided. No nights or weekends required. Flexible Read more
*Apple* Certified Mac Technician - Updated 6...
…and friendly, hands-on technical support to customers troubleshooting and repairing Apple /Mac products with courtesy, speed and skill. Use your problem-solving skills Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.