Contents:

• PHP Background
• Getting Started
• PHP Variables
• PHP File and Variable Naming Conventions
• PHP and HTML Output Basics
• Catching Errors
• If-Then Statements
• Arrays
• Basic Statements
• Looping Through Arrays
• Functions
• Obtaining Form Input
• GET and POST in a Simple Math Example
• Types of HTML Form Widgets
• Basic PHP Form Processing
• A Sample PHP-HTML Template
• Basic File I/O
• A Page That Changes Each Time
• Related Resources

PHP Background   [top]
PHP started as a set of Perl scripts created by Rasmus Lerdorf in 1995, who named this set of scripts 'Personal Home Page Tools'. It was eventually implemented in C and given the same acronym but with a recursive meaning - PHP: Hypertext Preprocessor. Today, PHP is being used by an estimated hundreds of thousands of developers, with several million sites reported as having it installed, which accounts for over 20% of all domains on the Internet.

Getting Started   [top]
Our PHP scripts will live on the ITP Stage server (stu.itp.nyu.edu). A PHP script can be executed using the command-line while logged into the server, but for our purposes, they will primarily be executed by a web user over the Internet. All your PHP scripts should have a ".php" extension, i.e. "hello.php" or "my_pix.php" and can contain HTML, Javascript, and of course, PHP. In fact, a ".php" file can contain only HTML and still display fine, but if your file contains actual PHP code, then it must have a ".php" extension to execute properly.

Here's a few things to know about making PHP statements, comments, and formatting the code:

• PHP is free form - whitespace doesn't matter. Most people like to use liberal indentation, but you could write all on one line, if you're into that kind of thing.
• All PHP statements end in a ; (semicolon), like C or Perl.
• Comments begin with # (pound sign) or //
• Everything after the # (or //), and up to the end of the line is ignored, and the # (or //) needn't be at the beginning of the line.
• To comment out blocks of code, you can use "/*" to start the comment and "*/" to end.

PHP is often interspersed with HTML and as such needs it's own set of delimiters to say which parts of the document are PHP blocks. This syntax is:

<?php
# This is a comment in PHP
print "What a stupid example!";
?>

Did you see the # in front of the comment? Did you also see the ; that ends the next line? This is because the first line is a comment, and the 2nd line is an actual statement. When you use the print command, you're sending that text straight to the browser over the web.

PHP Variables   [top]
PHP has several different data types. The most common are scalars which hold a single value, and arrays which can hold multiple values. The character of the realm with variables is $ (dollar sign). It signifies a variable that can hold a single value or a set of values, and these values can be numbers or strings, or even references to other variables. Here some common uses of variables as scalars:

$answer = 40;	# Integer
$Answer = 41;	# PHP is case-sensitive
$ANSWER = 42;	# PHP is still case-sensitive
$pi = 3.1417;	# Decimal
$animal = "dog";	# Text
$animal = 'dog';	# Using single or double quotes to denote your string
$animal_text = "dog \n cat \n mouse\n"; # Putting line breaks in your string

Remember: PHP is case-sensitive, so keep that in mind. You might try keeping all my variables in lower-case. It's one less thing you have to worry about. This is one tip that I keep forgetting when I write my scripts.

PHP excels when it comes to strings and text, so it's easy to concatenate text together of drop the value of a variable inside another. You can either drop them in specific places in the text, or you can build them using the '.' operator.

$x = 3;
$y = 8;
$sum = $x + $y;
$response = "The sum of $x and $y is $sum\n";
print $response;

# I could also have just explicitly printed the response:
print "The sum of $x and $y is $sum\n"

# Remember Mad Libs?
$adj1 = "dark";
$adj2 = "stormy";
$noun1 = "night";

print "Chapter One: It was a $adj1 and $adj2 $noun1\n";

print 'Chapter One: It was a '.$adj1.' and '.$adj2.' '.$noun1.'\n';

# Building a name using the . operator
$firstname = "Daniel";
$lastname = "Rozin";
$fullname = $firstname." ".$lastname;

# I could have also written:
$fullname = "$firstname $lastname";

print "I know an art god named $fullname\n";

print "The \"Big Mac\" now costs \\\$2 due to lower interest rates and national obesity\n";

PHP File and Variable Naming Conventions   [top]
PHP likes to see file and variable names that are alphanumeric, or in PHP syntax [a-z0-9]. In filenames, you'll often see the use of the underscore "_" and the dash "-":

hello.php
first_ass.php   # The ass is short for assignment, silly
second-ass.php  # The ass is still short for assignment
ass2.php        # The ass is short for, well, you get the picture
2ass.php        # ... see above ...

-new-ass.php

http://itp.nyu.edu/~[netId]/dwd/hello.php

For variables, much of the same naming conventions apply, except the dash "-" should never be used, since this also means the minus sign:

$title = "First Assignment";              # Fine
$first_ass_title = "First Assignment";    # Fine
$second-ass-title = "Second Assignment";  # No good
$ass2_title = "Second Assignment";        # Fine

\$2nd_ass_title = "Second Assignment";  # No good

PHP and HTML Output Basics   [top]
The whole point of using PHP to make web pages is that you can easily inject the values of PHP variables or make decisions about what blocks of HTML to print and have the PHP and HTML live in the same document. A simple PHP shortcut is this syntax:

<?php
$name = "Chris";
?>

The stupidest name I can think of is <b> <?= $name ?> </b>

so to quickly sub a PHP value in HTML, use the <?=$name_of_var?> syntax.

Of course, all of this can be done without leaving PHP:

<?php
$name = "Chris";

print "The stupidest name I can think of is <b> {$name} </b>";
?>

In this case, we just used a print statement and encased the variable in braces in the text. The braces are optional but are important if you need a variable to abut against some other text:

<?php
$closing_time = "4:00";

print "Closing time is {$closing_time}am";
?>

One other method I find very handy is the echo() method which, while very similar to the print() method, also lets you define a label at the beginning of the text you want to print, and then lets you mix HTML and PHP variables until you write the label once more (in this case "END" is the label). This is known as the heredoc syntax:

but watch out as it is finicky about whitespace - the opening label (in this case "END"), must be followed immediately by a newline, and the end label (in this case "END") must appear at the very beginning of its line and must be the only statement on that line

<?php
$prof_name = "Chris";
$my_name = "Bob";
$excuse = "my dog pressed control-alt-delete on my PowerBook";
$late_day = "Friday";

echo <<<END
Dear $prof_name,<br>
<p>
This is $my_name writing you.  I am really sorry but I couldn't do my assignment.
Unfortunately, $excuse, so I'll have for you by $late_day.
<p>
Sorry about that,<br>
$my_name
END;
?>

<?php

echo <<<END
  This is a statement I want to print
  END;

if ($cmd=="print it")
{ echo <<<END
  This is a statement I want to print
END; }
?>

<?php

echo <<<END
  This is a statement I want to print
END;

if ($cmd=="print it")
{ echo <<<END
  This is a statement I want to print
END;
}
?>

<?php
$prof_name = "Chris";
$my_name = "Bob";
$excuse = "my dog pressed control-alt-delete on my PowerBook";
$late_day = "Friday";
?>

Dear <?=$prof_name?>,<br>
<p>
This is <?=$my_name?> writing you.  I am really sorry but I couldn't do my assignment.
Unfortunately, <?=$excuse?>, so I'll have for you by <?=$late_day?>.
<p>
Sorry about that,<br>
<?=$my_name?>

Catching Errors   [top]
PHP on Stage is configured to reveal minimal information when errors occur, so we need to have two-pronged approach. The following lines will help us catch a variety of errors, especially when we start connecting to our database:

error_reporting(E_ALL ^ E_NOTICE);
ini_set('display_errors', 1);

php test.php

If-Then Statements   [top]
You can create a lot of great stuff simply through setting variables and using If-Then statements to control the flow of your logic. The basic format is:

if ([some condition is true])
{	# Create some functionality here
}
elseif ([some other condition is true])
{	# Create some other functionality here
}
else
{	# Use this if you need to catch all the other cases
}

Common tests in an if statement are:

# Comparing numbers using "=="
if ($age==10)
{	# Integer equality test
	print "You are 10 years old!\n";
}
if ($age!=10)
{	# Integer inequality test
	print "You are not 10 years old.\n";
}
if ($age>10)
{	# Integer greater than test
	print "You are greater 10 years old.\n";
}
if ($age<10)
{	# Integer less than test
	print "You are less than 10 years old.\n";
}

# Comparing strings using "=="
if ($favorite_team=="Yankees")
{	# String equality
	print "Get me a giant foam hand the next time you're at the Stadium.\n";
}
if ($favorite_team!="Yankees")
{	# String inequality
	print "Not a Yankees fan, eh?  I am a Mets fan myself.  Oy!\n";
}

# Comparing strings using strcmp()
if (!strcmp($name,"Eli"))
{	# String equality
	print "You have the same name as the NY Giants QB.\n";
}
elseif (strcmp($name,"Eli")>0)
{	# $name is greater than Eli
	print "Your name is lexically greater than the Giants QB.\n";
}
else
{	# $name is less than Eli
	print "Your name is lexically lesser than the Giants QB.\n";
}

# Comparing strings case-independently using strcasecmp()
if (!strcasecmp($name,"Eli"))
{	# String equality
	print "Your name could be Eli, eli, eLi, eLI.\n";
}

# Using the empty() function to determine if a value was given
if (empty($favorite_team))
{	# Blank value
	print "Hmm... you don't seem to have a favorite team.\n";
}
if (!empty($favorite_team))
{	# Non-blank value - means that something is there
	print "Hooray!  You have a favorite team.\n";
}

Arrays   [top]
As for arrays, an array is just an ordered set of scalars. It could be numbers, strings, or you can have both in the same list. Arrays can either be indexed by number (often called a "normal" array), or by a string (commonly called an "associative array" or a "hash"). Here's the firstnames of the Beatles in a normal array:

# Array Indexed by Number or Normal Array
$beatles = array("John","Paul","George","Ringo");

# Another way to define the same thing
$beatles[0] = "John";
$beatles[1] = "Paul";
$beatles[2] = "George";
$beatles[3] = "Ringo";

# Array Indexed by String or Associative Array
$beatles_fullnames = array(
	"John"   => "John Lennon",
	"Paul"   => "Paul McCartney",
	"George" => "George Harrison",
	"Ringo"  => "Ringo Starr"
);

# Another way to define the same thing
$beatles_fullnames["John"] = "John Lennon";
$beatles_fullnames["Paul"] = "Paul McCartney";
$beatles_fullnames["George"] = "George Harrison";
$beatles_fullnames["Ringo"] = "Ringo Starr";

Note that normal arrays use brackets around the index (i.e. [0] or [1]) and the first index is 0. Associative arrays also use brackets around the index (i.e. ["John"] or ["Paul"]).

Basic Statements   [top]
PHP has all of the basic programming constructs of other languages. Let's look at this example:

<?php

# Make sure we display errors to the browser
error_reporting(E_ALL);
ini_set('display_errors', 1);

# Array Indexed by Number or Normal Array
$beatles = array("John","Paul","George","Ringo");

# Let's loop through and find the Beatle
$i = 0;
foreach ($beatles as $firstname)
{	if ($firstname=="John")
	{	print "I found John!  He's at $i <br>\n";
	}
	elseif ($firstname=="Paul")
	{	print "I found Paul!  He's at $i <br>\n";
	}
	elseif ($firstname=="George")
	{	print "I found George!  He's at $i <br>\n";
	}
	elseif ($firstname=="Ringo")
	{	print "I found Ringo!  He's at $i <br>\n";
	}
	else
	{	print "Hmm, apparently there's a 5th Beatle... <br>\n";
	}
	
	$i++;
}

?>

$beatles = array("John","Paul","George","Ringo");

foreach ($beatles as $firstname)
{	print "$firstname\n";
}

$beatles = array("John","Paul","George","Ringo");

for($i=0; $i<count($beatles); $i++)
{	print "index $i is $beatles[$i] \n";
}

$beatles_fullnames = (
	"John"   => "John Lennon",
	"Paul"   => "Paul McCartney",
	"George" => "George Harrison",
	"Ringo"  => "Richard Starkey"
);

foreach ($beatles_fullnames as $nickname => $fullname)
{	print "$nickname is the nickname of $fullname \n";
}

################################################
# Add HTML bold tags to a string
################################################
function bold_this($input)
{
  $local_string = "<b>" . $input . "</b>";
  return ($local_string);
}

$original_string = "The Boldly Dan O'Sullivan";

# Put newly bolded version in its own variable
$newly_bolded_string = bold_this($original_string);

# The original variable will now hold the bolded version
$original_string = bold_this($original_string);

$name = "The Boldly Dan O'Sullivan";

print "The boldest dude I know is ". bold_this($name) . "<p>";

http://itp.nyu.edu/~[netId]/dwd/foo.php?name1=value1&name2=value2

or

http://itp.nyu.edu/~[netId]/dwd/class02-ttt.php?v1=x&v5=o&v9=x

or

http://itp.nyu.edu/~cs220/dwd/class02-math1.php?x=2&y=5&cmd=add

<form></form>
<form action="$script_name" method="POST" enctype="application/x-www-form-urlencoded">
Creates all forms

<select name="NAME"></select>
<select name="state_id"></select>
Creates a pulldown menu 

<option value="VALUE" [selected]>NAME
<option value="1">Delaware
<option value="2" selected>Massachusetts
Sets off each menu item 

<textarea name="NAME" cols=40 rows=8></textarea>
<textarea name="new_blog_message" cols=40 rows=8>A paragraph could go</textarea>
Creates a text box area. Columns set the width; rows set the height. 

<input type="checkbox" name="NAME" checked>
<input type="checkbox" name="subscribed">Check here if you wish to receive our newsletter
Creates a checkbox. Text follows tag. 

<input type="radio" name="NAME" value="VALUE" [checked]>
<input type="radio" name="likes_ice_cream" value="Yes">Yes
<input type="radio" name="likes_ice_cream" value="No" checked>No
<input type="radio" name="not_good_with_napkins" value="1" checked>Yes
<input type="radio" name="not_good_with_napkins" value="0">No
Creates a radio button. Text follows tag 

<input type="text" name="NAME" value="VALUE" size=20>
<input type="text" name="firstname" value="Christopher" size=20 maxlength=128>
Creates a one-line text area. Size sets length, in characters.

<input type="password" name="NAME" value="VALUE" size=20>
<input type="password" name="pw" value="" size=20 maxlength=128>
Same as a text field except that asterisks are shown instead of actual chars.

<input type="submit" name="NAME" value="VALUE">
<input type="submit" name="dataAction" value="Submit">
Creates a Submit button

<input type="hidden" name="NAME" value="VALUE">
<input type="hidden" name="cart_id" value="4F3HDGS36251">
Creates a hidden field that you can use to hold text.  Not visible to user. 

<input type="image" border=0 name="NAME" src="images/home/submit_b.gif">
Creates a Submit button using an image 

<input type="reset">
Creates a Reset button 

<form action="login.php" method="POST" enctype="application/x-www-form-urlencoded">
Username: <input type="text" name="un" value="" size=20 maxlength=32> <br>
Password: <input type="password" name="pw" value="" size=20 maxlength=32> <br>
<input type="submit" name="dataAction" value="Login">
</form>

$submitName = "dataAction";
$submitValue = "Submit";

if ($_POST[$submitName]==$submitValue)
{	# Form was submitted so do whatever processing is needed here

}

<input type="submit" name="<?=$submitName?>" value="<?=$submitValue?>">

<?php

#########################################################
# template.php - Base template for PHP script
#########################################################
$scriptName = $_SERVER['PHP_SELF'];
$pageTitle = "put the title of your web page here";

# Make sure we display errors to the browser
error_reporting(E_ALL ^ E_NOTICE);
ini_set('display_errors', 1);
?>

<html>
<head>
<title><?=$pageTitle?></title>
<style type="text/css">
body {
	font: 13px arial;
	color: #000;
	background-color: #fff;
	padding: 10px;
	margin: 0px;
}
</style>
</head>
<body>
<b><?=$pageTitle?></b>
<p>
<form action="<?=$scriptName?>" method="POST" enctype="application/x-www-form-urlencoded">
</form>
</body>
</html>

$file = "/home/[netId]/public_html/foo.txt";

# Test if the file physically exists on the server
if (file_exists($file))
{	print "The file $file exists";
}

$file = "/home/[netId]/public_html/foo.txt";

$content = file_get_contents($file);
print "Content is $content";

$file = "/home/[netId]/public_html/foo.txt";

$file_ptr = fopen($file,"r"); # "r"=read, "a"=append, "w"=overwrite
while (!feof($file_ptr))
{	$line = fgets($file_ptr);
	print "$line <br>";
}

$file = "/home/[netId]/public_html/foo.txt";
$text = "This is some text I want to save";

$file_ptr = fopen($file,"a"); # "a" = append to existing content, "w" = overwrite
fwrite($file_ptr,$text);
fclose($file_ptr);