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PHP

By W. Jason Gilmore

ABOUT THIS REFCARD

PHP is the world's most popular server-side Web scripting language, sporting a syntax simple enough to attract novice programmers yet powerful enough to run some of the world's most popular websites, among them Yahoo!, Facebook, GameSpy, and Vimeo.

This reference card was created to help you quickly navigate some of PHP's most commonplace features, including objectoriented programming, array and string manipulation, regular expressions, and MySQL integration.

PHP's behavior can be configured at a variety of levels:

Global Configuration

The php.ini file is PHP's configuration fi le, containing more than 200 directives capable of tweaking nearly every aspect of the language's behavior. This fi le is parsed every time PHP is invoked, which for the server module version occurs only when the web server starts, and every time for the CGI version.

Host- and Directory-specific Confi guration

If you lack access to the php.ini fi le, you may be able to change desired directives within Apache's httpd.conf or .htaccess files. For instance, to force the display of all PHP errors for solely your development domain (for instance http://dev.wjgilmore.com), add the following to a .htaccess file:

php_fl ag display_errors on

Script-specific Configuration Occasionally you'll want to tweak directives on a per-script basis. For instance to change PHP's maximum allowable execution time for a script tasked with uploading large fi les, you could call the ini_set() function from within your PHP script like so:

ini_set('max_execution_time', 60);

Changing the PHP File Extension

PHP's default fi le extension is .php, however you can change it to whatever you please by adding the desired extension to the AddType directive within Apache's httpd.conf fi le. For instance to configure Apache to recognize .dzone as a supported PHP file extension:

AddType application/x-httpd-php .php .dzone

POPULAR PEAR PACKAGES

The PHP Extension Application Repository (PEAR) is the de facto service for distributing reusable PHP components. Over 500 packages are available for download from http://pear.php.net/, including these popular solutions:

POPULAR FRAMEWORKS

Web frameworks help the programmer to embrace best practices, simultaneously decreasing errors and eliminating redundant code. If you haven't yet settled upon a framework, consider checking out one or several of the following popular solutions:

OBJECT-ORIENTED PHP

Creating a Class

A class defines the behavior and characteristics of an entity you'd like to represent in an application. A sample class follows:

class RadioStation {
private $_id;
private $_name;
private $_frequency;
private $_band;
private $_audioStream;
public function setBand($band) {
$this->_band = $band;
}
public function getBand() {
return $this->_band;
}
...
}

Object Instantiation

To create an instance of a class (known as an object), you call the class name like you would a function, preceding it with the new keyword:

$wtvn = new RadioStation();

Class Constructors

Constructors are useful for performing initialization tasks at class instantiation time, thereby saving you the hassle of calling additional class methods. Constructors are declared using the __construct() method, like so:

function __construct($id="") {
// If specifi c station ID is requested, retrieve it
from the database
if (isset($id))
$this->fi nd($id);
}

Class Destructors

Custom class destructors can perform tasks when the object is destroyed. You can create a destructor using the __destruct() method:

function __destruct() {
printf("The radio station %s has been destroyed!",
$this->name);
}

Attribute and Method Visibility

PHP supports three levels of attribute and method visibility:

Class Constants

Class constants are defi ned with the const keyword, and can be referenced through the scope resolution operator (::). For instance, to define a constant identifying the RadioStation class' minimum supported PHP version:

const MIN_PHP_VER = '5.3';

You can then reference it outside the class like so:

echo RadioStation::MIN_PHP_VER;

Extending Classes

Class hierarchies can be created using the extends keyword. For instance, an application tasked with cataloging all major media outlets might first define a MediaOutlet class which defines some broad characteristics, and then child classes such as RadioStation and TVStation would inherit from it:

class MediaOutlet {
protected $owner;
protected $residentCountry;
public function setOwner($owner) {
...
}
}
class RadioStation extends MediaOutlet {
...
}

If you wanted to prevent child classes (in this case, RadioStation) from overriding a parent method, prefix it with the final keyword. For instance:

final public function setOwner($owner) {
...
}

Class Abstraction

The aforementioned MediaOutlet class would be more accurately defi ned as an abstract class, because it would never be explicitly instantiated (instead, one would instantiate derived classes such as RadioStation, TVStation, Newspaper, etc.). Abstract classes are declared using the abstract keyword:

abstract class MediaOutlet {
...
}

You can choose to override any methods found within an abstract class, which would then be inherited by its child classes, or alternatively you can declare them as abstract, requiring these methods be defined by any child.

Creating Interfaces

An interface helps developers rigorously enforce application specifications, and is similar to an abstract class, but contains solely the required method signatures. Any class implementing the interface must also implement all defined interface methods.

Interfaces are defined using the interface keyword and their names are typically prefixed with a capital I:

interface IRadioStation {
public function setBand($band);
public function getBand();
}
class RadioStation implements IRadioStation {
...
}

WORKING WITH ARRAYS

The array is one of programming's most powerful data structures, capable of managing a seemingly endless variety of data.

Creating an Array

The following two examples all create an array named $stations consisting of three elements:

$stations = array (
"WTVN",
"WBNS",
"WYTS");

$stations = array();
$count = array_push($stations, "WTVN", "WBNS", "WYTS");

You can create an array consisting of a character- or numericallybased range using the range() function:

// $teenListenerDemographic =
// array(13,14,15,16,17,18,19)
$teenListenerDemographic = range(13,19);

Retrieving Array Contents

Indexed arrays such as those created so far can be accessed according to their numerical offset (beginning with a zerobased offset). For instance to retrieve the second value in the $stations array:

$callSignal = $stations[1];

Perhaps the most flexible way to enumerate array contents is through the foreach statement:

foreach($stations AS $station)
printf("%s<br />", $station);

Associative Arrays

Associative arrays give developers the opportunity to assign meaningful context to both the array value and its corresponding key:

$stations = array(
"WTVN" => "610",
"WBNS" => "1460",
"WYTS" => "1230 "
);

You can then obtain a value (in this case the station/band) by referencing its call signal:

// $channel = "610"
$channel = $stations["WTVN"];

The foreach statement proves equally useful for navigating associative arrays:

foreach($stations AS $key => value)
printf("%s => %s<br />", $key, $value);

Multidimensional Arrays

Multidimensional arrays are useful for representing more complex data structures:

$stations = array(
"AM" =>
array("WTVN" => "610",
"WBNS" => "1460",
"WYTS" => "1230"),
"FM" =>
array("WLVQ" => "96.3",
"WNCI" => "97.9")
);

Referencing an element isn't unlike the methods used for indexed and associative arrays; it's just a tad more verbose:

$channel = $stations["FM"]["WTVN"];

Determining Array Size

The number of elements found in an array can be determined using the count() function:

// Outputs "3 stations are being tracked"
printf("%d stations are being tracked",
count($stations));

Sorting Arrays

PHP offers a powerful assortment of functions (more than 70) capable of sorting arrays in a variety of ways. Most of these functions accept an optional parameter which can change the sorting behavior. Four values are supported, including SORT_ REGULAR for comparing elements without implicit typecasting, SORT_NUMERIC for comparing elements numerically, SORT_STRING for comparing elements as strings, and SORT_LOCALE_STRING, for sorting elements according to the defined locale.

Consult the PHP manual for a complete listing: http://www.php.net/array.

STRING PARSING

PHP supports over 100 functions identified as specific to string parsing and manipulation. Following are the most commonly used tasks.

$stations = array("WTVN","WBNS","WYTS");
$stations = implode(",", $stations)
// $stations = "WTVN,WBNS,WYTS"

$stations = "WTVN,WBNS,WYTS";
$stations = explode(",", $stations);
// $stations[0]="WTVN", $stations[1]="WBNS",
$stations[2]="WYTS"

$sentence = "Columbus is home to numerous
radio stations";
$words = str_word_count($sentence);
// $words = 7

$callsign = strtoupper("wtvn");
// $callsign = "WTVN"

$input = "You won the <a href="http://www.
example.com">lottery!</a>."
$clean = strip_tags($input);
// $clean = "You won the lottery!"

$phrase = "Big rockers listen to rock radio";
$phrase = str_replace("rock", "talk", $phrase);
// $phrase = "Big talkers listen to talk radio"

$description = "WFAN: Sports Radio 66";
$callsign = substr($description, 0, 4);

if (strcasecmp("WTVN", "wtvn") == 0)
echo "The strings are equal in a caseinsensitive
context."

$stations = "WTVN: 610\nWLW: 700\nWYTS: 1230";
$html = nl2br($stations);
// $html = "WTVN: 610<br />WLW: 700<br />WYTS:
1230"

Regular Expressions

PHP's regular expression features borrow heavily from both the Perl and POSIX formats, and in fact are formally identified as such.

Perl-compatible (PCRE) Regular Expression Functions

PHP supports eight PCRE-specific functions, including these commonly used solutions:

Common PCRE Pattern Modifiers

Metacharacters

POSIX Regular Expression Functions

PHP supports seven functions as defi ned by the POSIX 1003.2 specifi cation, including these commonly used solutions:

POSIX Regular Expression Syntax

Regular Expression Examples

Validating a Phone Number

Presumes the required format is XXX-XXX-XXXX.

// PCRE
if (preg_match('/^[2-9]{1}\d{2}-\d{3}-\d{4}$/', '614-
599-2599'))
echo "Valid number!";
// POSIX
if (ereg('^[2-9]{1}[0-9]{2}-[0-9]{3}-[0-9]{4}$', '614-
999-2599'))
echo "Valid number!";

Validating a Username

Presumes username is between 6 and 10 alphabetical and numerical characters.

// PCRE
if (preg_match('/^[a-z0-9]{6,10}$/i', '800gilmore'))
echo "Valid username!";
// POSIX
if (eregi('^[a-z0-9]{6,10}$', '800gilmore'))
echo "Valid username!";

Turn URLs into hyperlinks

// PCRE
$text = "Go to http://www.wjgilmore.com.";
$html = preg_replace('/\s(\w+:\/\/)(\S+\.?)(\w+)/',
' <a href="\\1\\2\\3">\\1\\2\\3</a>', $text);
// POSIX
$text = "Go to http://www.wjgilmore.com. ";
$html= ereg_replace('[a-zA-Z]+://(([.]?[a-zAZ0-
9_/-])*)', '<a href="\\0">\\0</a>', $string);
// $html = "Go to <a href=" http://www.wjgilmore.
com">http://www.wjgilmore.com."

Telling Time with PHP

The Date Function

The date() function is perhaps one of PHP's most commonly used functions, capable of retrieving nearly every temporal attribute of a specific timestamp.

string date(string $format [, $int $timestamp])

Day Parameters

Week Parameters

Month Parameters

Year Parameters

Date Function Examples

Setting the Timezone

You can set the timezone for all scripts by setting the date. timezone configuration directive within the php.ini file, or on a per-script basis using the date_default_timezone_set() function.

Other Useful Functions

PHP 5.1.0 introduced an object-oriented DateTime class. See http://www.php.net/DateTime for more information.

Date-related Examples

MYSQL Integration

Although PHP supports several popular databases, MySQL remains by far the most common database solution. PHP's MySQL support has evolved considerably in recent years, with the MySQLi (MySQL Improved) extension being the current recommended solution. Here are the most commonly used methods.

Connecting to MySQL

The mysqli extension provides a number of ways to connect to MySQL, but the easiest involves just passing the connection data along when instantiating the mysqli class:

mysqli new mysqli([string host [, string user [, string
pswd
[string dbname [int port [string socket]]]]]]);
Here's an example:
$mysqli = new mysqli("localhost", "webuser", "secret",
"corporate");

Handling Connection Errors

In case of connection error you can retrieve both the error number and error string using the errno() and error() methods. Example:

if ($mysqli->errno) {
printf("Unable to connect: %s", $mysqli->error);
exit();
}

Sending a Query to the Database

Once the connection has been established, you can begin querying the database. Queries are sent using the query() method:

mixed query(string $query [, int $resultmode])

Setting the optional $resultmode parameter to MYSQLI_USE_ RESULT will cause query() to return the result as an unbuffered set.

Example:

$result = $mysqli->query("SELECT callsign FROM
stations");

Sending INSERT, UPDATE, and DELETE queries works identically. For instance, sending an UPDATE query works like this:

$result = $mysqli->query("UPDATE stations SET station
= '610' WHERE callsign = 'WTVN'");

Retrieving Data

Data can be parsed from the result set using a number of data structures, including via associative and indexed arrays, and objects.

Retrieving data as an associative array:

while ($row = $result->fetch_array(MYSQLI_ASSOC) {
printf("%S", $row["callsign"]);
}

Retrieving data as an indexed array:

while ($row = $result->fetch_row() {
printf("%S", $row[0]);
}

Retrieving data as an object:

while ($row = $result->fetch_object() {
printf("%S", $row->callsign);
}

Determining the Number of Rows Affected and Retrieved

To determine the number of affected rows after sending an INSERT, UPDATE, or DELETE query, use the affected_rows property.

Example:

$result = $mysqli->query("UPDATE stations SET station =
'610' WHERE callsign = 'WTVN'");
printf("Rows affected: %d", $result->rows_affected);

To determine how many rows were returned when using a SELECT query, use the num_rows property:

$result = $mysqli->query("SELECT * FROM stations WHERE
state ='Ohio');
printf("Rows affected: %d", $result->num_rows);

Working with Prepared Statements

Prepared statements both optimize query performance and decrease the possibility of SQL injection attacks by separating the query data from the logic, fi rst passing the query to MySQL for preparation, binding variables to the query columns, and fi nally passing the data to MySQL for query execution.

To prepare a query, create the query, and then initialize a statement object using the stmt_init() method:

$query = "INSERT INTO stations VALUES(?, ?)";
$stmt = $mysqli->stmt_init();

Next the query is prepared by passing it to MySQL using the prepare() method:

$stmt->prepare($query);

Next, bind the parameters using the bind_param() method:

$stmt->bind_param('ss', "WTVN", "610");

Finally, execute the prepared statement using the execute() method:

$stmt->execute();

You can also use prepared statements to retrieve results. The general process used to execute the previous INSERT query is identical to that required for executing a SELECT query, except that the bind_param() method is not required, and you bind results following a call to the execute() method. An example follows:

$query = "SELECT callsign, frequency FROM stations
ORDER BY callsign";
$stmt = $mysqli->stmt_init();
$stmt->prepare($query);
$stmt->execute();
$stmt->bind_result($callsign, $frequency);
while ($stmt->fetch())
printf("%s: %s<br />", $callsign, $frequency);

Transactions

By default the MySQLi extension will render each query "permanent" upon successful execution, actually changing the database's contents when INSERT, UPDATE, and DELETE queries are processed. However the success of some tasks depend upon the successful execution of several queries, and until all have occur. ATM transactions and online credit card processing are common examples requiring several queries. Using transactions, you can change the MySQLi extension's behavior, committing a series of queries as you see fit.

To begin a transaction, start by disabling the autocommit feature:

$mysqli->autocommit(FALSE);

Execute the various queries as you see fit, and if everything proceeds as you expect, execute the commit() method:

$mysqli->commit();

Otherwise, if a problem occurs, execute the rollback() method:

$mysqli->rollback();

USEFUL ONLINE RESOURCES

About The Author

W. Jason Gilmore

Jason Gilmore is founder of W.J. Gilmore, LLC, providing web development, consulting, and technical writing services to clientele ranging from publicly traded corporations to small startups. Jason is a prolific contributor to a number of leading publications such as Developer.com, Linux Magazine, and TechTarget, with almost 100 articles to his credit. He's cofounder of the CodeMash conference ( http://www.codemash.org/), a non-profit organization charged with organizing the annual namesake event.

Publications

• Beginning PHP and MySQL
• Beginning PHP and PostgreSQL 8 with Robert H. Treat
• Beginning PHP and Oracle

Website

• http://www.wjgilmore.com

Recommended Book

Beginning PHP and MySQL is the definitive book on the PHP language and MySQL database. Readers are treated to comprehensive introductions of both technologies, and in addition to in-depth instruction regarding using these two technologies in unison to build dynamic web sites.

---

BUY NOW

books.dzone.com/books/phpsql

Comments

extprofile_firs... replied on Sun, 2008/10/05 - 6:52pm

Hello Mr. Gilmore—

there’s a minor bug on pg. 2 of the refcard. The equality operator does not belong into the function declaration, there has to be an assignment operator.

// Wrong:
function __construct($id=="") {

// Correct:
function __construct($id="") {

Kind regards,
Willy Dee.

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Jill Tomich replied on Mon, 2008/10/06 - 11:56am in response to: willydee

Hello Willy Dee,

Thanks for taking the time to download, review, and provide feedback on the PHP refcard. I've passed along your feedback to the author, and we are working to correct the error. A new version of the PHP refcard will be available within the next couple of days.

With Kind Regards,

Jill 

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Jill Tomich replied on Tue, 2008/10/07 - 2:18pm

We've had some feedback on the PHP refcard from the community, and have updated it to reflect a few edits to fix some errors. The new version is now available. Go here and click on "Click Here to Download PDF" to download the new version.

What's changed:

• Page 2, Column 1 - Under the section "Class Constructors", the first line has been changed to read:
  
  function __construct($id="") {
  
  In addition, there was a formatting issue regarding the double underscores in the same section, and the section that follows it. They have been changed to reflect one contiguous long underscore.

• Page 3, Column 1, 1st Table - Under the "Creating an Array" section, the following was deleted:
  
  $stations << "WTVN";
  $stations << "WBNS";
  $stations << "WYTS";
  
  It is not valid PHP.

Thanks to those who have provided feedback.

-- Jill

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Jill Tomich replied on Thu, 2008/10/09 - 2:10pm

Hi Folks,

Well, it seems we missed an edit in that table on page 3. A new version of the PHP refcard is available. Go here and click on "Click Here to Download PDF" to download the new version. My apologies for the mistakes. This version is correct.

-- Jill

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Ken Guest replied on Fri, 2008/10/10 - 6:22pm

phpunit has been hosted on phpunit.de instead of pear.php.net since around 2006-06-29. The last version released on pear.php.net was version 2.3.6! (Version 3.3.1 is the most current). Could you please revise your PDF to correct this? Pointing people to a very old version of PHPUNit would only serve to confuse them! Thank you.

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Jill Tomich replied on Fri, 2008/10/10 - 7:19pm in response to: kenguest

Thanks for the feedback. We will make the correction, and update the PDF as soon as possible. I'll post a note here when it has been updated.

Thanks again,

Jill 

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Evan Ghosh replied on Sat, 2011/01/08 - 1:50am

One thing we all know about PHP is the fact that apparently, this is the most reputed and popular server side web scripting language. All around the world, people depend on PHP for the above mentioned reason. Much of that is because of the vast array of features that it offers that includes, PEAR packages, Regular expressions, Object Oriented PHP, MySQL Orientation and so on. Anyway, an update is very much necessary as other web scripting languages are catching pace!

Evan Ghosh

Research Development

Multivariate Testing

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Rocky Singh replied on Thu, 2011/10/20 - 2:43am

template

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