PHP

A quick introduction to PHP.

wikipedia:PHP [1]
Practical PHP Programming [2] by Paul Hudson.

Started out as Personal HomePage.
Now the PHP Hypertext Preprocessor.
Mostly server-side, like JSP.
LAMP [3]

Hello World.

<html>
<head>
<title>Hello</title>
</head>
<body>
<?php
print 'Hello, World!';
?>
</body>
</html>

All variables start with $
Double quotes evaluate variables. First one works:

<html>
<head>
<title>Hello</title>
</head>
<body>
<?php
  $name = "Joe";
  print "Hello, $name";
  print 'Hello, $name';
?>
</body>
</html>

Dynamic typing and conversion:

<?php
   $mystring = "12";
   $myinteger = 20;
   print $mystring + $myinteger;
?>

Can also typecast:

<?php
   $mystring = "wombat";
   $myinteger = (integer)$mystring
?>

Strings act as arrays:

<?php
   $mystr = "Jello, world?";
   $mystr{0} = "H";
   $mystr{12} = "!";
   print $mystr;
?>

Is it set?

<?php
   $foo = 1;
   if (isset($foo)) {
      echo "Foo is set\n";
   } else {
      echo "Foo is not set\n";
   }

   if (isset($bar)) {
      echo "Bar is set\n";
   } else {
      echo "Bar is not set\n";
   }
?>

Name	Value
HTTP_REFERER	If the user clicked a link to get the current page, this will contain the URL of the previous page they were at, or it will be empty if the user entered the URL directly.
HTTP_USER_AGENT	The name reported by the visitor's browser
PATH_INFO	Any data passed in the URL after the script name
PHP_SELF	The name of the current script
REQUEST_METHOD	Either GET or POST
QUERY_STRING	Includes everything after the question mark in a GET request

<?php
   if (isset($_SERVER['HTTP_REFERER'])) {
      print "The page you were on previously was {$_SERVER['HTTP_REFERER']}<br />";
   } else {
      print "You didn't click any links to get here<br />";
   }
?>

<a href="refer.php">Click me!</a>

The backtick tells the OS to run a program:
```
print `ls`;
```

<?php
   function multiply($num1, $num2) {
      $total = $num1 * $num2;
      return $total;
   }

   $mynum = multiply(5, 10);
?>

Use & to pass by reference.

<?php
   function square1($number) {
      return $number * $number;
   }

   $val = square1($val);

   function square2(&$number) {
      $number = $number * $number;
   }

   square2($val);
?>

Or to return by reference:

<?php
   function &square1($number) {
      return $number * $number;
   }

   $val =& square1($val);
?>

Parameters can be given default values:

<?php
   function doFoo($Name = "Paul") {
      return "Foo $Name!\n";
   }

   doFoo();
   doFoo("Paul");
   doFoo("Andrew");
?>

Extra arguments are ignored, but can be retrieved:

<?php
   function some_func($a, $b) {
      for ($i = 0; $i < func_num_args(); ++$i) {
         $param = func_get_arg($i);
         echo "Received parameter $param.\n";
      }
   }

   function some_other_func($a, $b) {
      $param = func_get_args();
      $param = join(", ", $param);
      echo "Received parameters: $param.\n";
   }

   some_func(1,2,3,4,5,6,7,8);
   some_other_func(1,2,3,4,5,6,7,8);
?>

The scope of a variable is within the function it is in.
This prints out baz:

<?php
   function foo() {
      $bar = "wombat";
   }

   $bar = "baz";
   foo();
   print $bar;
?>

Functions can be passed as values and then invoked:

<?php
   $func = "sqrt";
   if (is_callable($func)) {
      print $func(49);
   }
?>

<?php
   $myarray = array("Apples", "Oranges", "Pears");
   $size = count($myarray);
   print_r($myarray);
   print $myarray[0];
?>

<?php
   $myarray = array("a"=>"Apples", "b"=>"Oranges", "c"=>"Pears");
   var_dump($myarray);
?>

Prints out:

array(3) {
   ["a"]=>
   string(6) "Apples"
   ["b"]=>
   string(7) "Oranges"
   ["c"]=>
   string(5) "Pears"
}

Access using $array["a"]

<?php
   for ($i = 0; $i < count($array); ++$i) {
      print $array[$i];
   }
?>

<?php
   while (list($var, $val) = each($array)) {
      print "$var is $val\n";
   }


   foreach($array as $val) {
     print $val;
   }

   foreach ($array as $key => $val) {
     print "$key = $val\n";
   }
?>

<?php
   $toppings1 = array("Pepperoni", "Cheese", "Anchovies", "Tomatoes");
   $toppings2 = array("Ham", "Cheese", "Peppers");
   $inttoppings = array_intersect($toppings1, $toppings2);
   $difftoppings = array_diff($toppings1, $toppings2);
   $bothtoppings = array_merge($toppings1, $toppings2);
   var_dump($inttoppings);
   var_dump($difftoppings);
   var_dump($bothtoppings);
?>

<?php
   function endswithy($value) {
      return (substr($value, -1) == 'y');
   }

   $people = array("Johnny", "Timmy", "Bobby", "Sam", "Tammy", "Danny", "Joe");
   $withy = array_filter($people, "endswithy");
   var_dump($withy);
?>

<?php
   $needle = "Sam";
   $haystack = array("Johnny", "Timmy", "Bobby", "Sam", "Tammy", "Danny", "Joe");
   if (in_array($needle, $haystack)) {
      print "$needle is in the array!\n";
   } else {
      print "$needle is not in the array\n";
   }
?>

ksort sort by keys, asort by values.

<?php
   $capitalcities['England'] = 'London';
   $capitalcities['Wales'] = 'Cardiff';
   $capitalcities['Scotland'] = 'Edinburgh';
   ksort($capitalcities);
   var_dump($capitalcities);
   asort($capitalcities);
   var_dump($capitalcities);
?>

<?php
   $array["a"] = "Foo";
   $array["b"] = "Bar";
   $array["c"] = "Baz";
   $array["d"] = "Wom";

   $str = serialize($array);
   $strenc = urlencode($str);
   print $str . "\n";
   print $strenc . "\n";
?>

<?php
   $arr = unserialize(urldecode($strenc));
   var_dump($arr);
?>

Define and use a class:

<?php
class dog {
   public function bark() {
      print "Woof!\n";
   }
}

class poodle extends dog {
   public function bark() {
      print "Yip!\n";
   }
}

$poppy = new poodle;
$poppy->bark();
?>

class dog {
   public $Name;

   public function bark() {
      print "Woof!\n";
   }
}

$poppy->Name = "Poppy";

//not this way:
$poppy->$Name = "Poppy";

To set class variables reference them using this.

function bark() {
   print "{$this->Name} says Woof!\n";
}

Public: This variable or function can be used from anywhere in the script
Private: This variable or function can only be used by the object it is part of; it cannot be accessed elsewhere
Protected: This variable or function can only be used by the object it is part of, or descendents of that class
Final: This variable or function cannot be overridden in inherited classes
Abstract: This function or class cannot be used directly - you must inherit from them first

class poodle extends dog {
   public function bark() {
      print "Yip!\n";
   }
   
   public function __construct($DogName) {
      parent::__construct($DogName);
      print "Creating a poodle\n";
   }

   public function __destruct() {
     print "{$this->Name} is no more...\n";
     parent::__destruct();
   }
}

The clone keyword copies all member variables and then calls __clone.

<?php
   abstract class dog {
      public function __clone() {
         echo "In dog clone\n";
      }
   }

   class poodle extends dog {
      public $Name;

      public function __clone() {
         echo "In poodle clone\n";
         parent::__clone();
      }
   }

   $poppy = new poodle();
   $poppy->Name = "Poppy";

   $rover = clone $poppy;
?>

== compares the objects' contents.
=== compares the objects' handles.

Just like Java.

<?php
   class employee {
      static public $NextID = 1;
      public $ID;

      public function __construct() {
         $this->ID = self::$NextID++;
      }
   }

   $bob = new employee;
   $jan = new employee;
   $simon = new employee;

   print $bob->ID . "\n";
   print $jan->ID . "\n";
   print $simon->ID . "\n";
   print employee::$NextID . "\n";
?>

This form:

<form action="someform.php" method="GET">
Name: <input type="text" name="Name" value="Jim" /><br />
Password: <input type="password" name="Password" maxlength="10" /><br />
Age range: <select name="Age">
<option value="Under 16">Under 16</option>
<option value="16-30" SELECTED>16-30</option>
<option value="31-50">31-50</option>
<option value="51-80">51-80</option>
</select><br /><br />
Life story:<br /> <textarea name="Story" rows="10" cols="80">Enter your life story here</textarea><br /><br />
<input type="radio" name="FaveSport" value="Tennis"> Tennis</input>
<input type="radio" name="FaveSport" value="Cricket"> Cricket</input>
<input type="radio" name="FaveSport" value="Baseball"> Baseball</input>
<input type="radio" name="FaveSport" value="Polo"> Polo</input>
<br />
<input type="checkbox" name="Languages[]" value="PHP" CHECKED> PHP</input>
<input type="checkbox" name="Languages[]" value="CPP"> C++</input>
<input type="checkbox" name="Languages[]" value="Delphi"> Delphi</input>
<input type="checkbox" name="Languages[]" value="Java"> Java</input>
<br /><input type="submit" />
</form>

would be handled with:

<?php
   $_GET['Languages'] = implode(', ', $_GET['Languages']);
   $_GET['Story'] = str_replace("\n", "<br />", $_GET['Story']);

   print "Your name: {$_GET['Name']}<br />";
   print "Your password: {$_GET['Password']}<br />";
   print "Your age: {$_GET['Age']}<br /><br />";
   print "Your life story:<br />{$_GET['Story']}<br /><br />";
   print "Your favourite sport: {$_GET['FaveSport']}<br />";
   print "Languages you chose: {$_GET['Languages']}<br />";
?>

Use setcookie to set and _COOKIE to read.

<?php
   if (!isset($_COOKIE['Ordering'])) {
      setcookie("Ordering", $_POST['ChangeOrdering'], time() + 31536000);
   }
?>

<form method="POST" action="mbprefs.php"> Reorder messages:
<select name="ChangeOrdering">
<option value="DateAdded ASC">Oldest first
<option value="DateAdded DESC">Newest first
<option value="Title ASC">By Title, A-Z
<option value="Title DESC">By Title, Z-A
</select>
<input type="submit" value=" Save Settings ">
</form>

Like Servlet sessions.
Start one with session_start().
Read and write session data with $_SESSION['var']
End with session_destroy()

<?php
//Connect to the database
   mysql_connect("localhost", "phpuser", "alm65z");
   mysql_select_db("phpdb");

//Send a query and get resutls
   $result = mysql_query("SELECT * FROM usertable");
   $numrows = mysql_num_rows($result);
   print "There are $numrows people in usertable\n";

//Use a variable in the query, just place it in.
   $result = mysql_query(
      "SELECT ID FROM webpages WHERE Title = '$SearchCriteria';");

//Free memory
   mysql_free_result($result);

//Close connection
   mysql_close();

?>

Very popular.
Easy to incrementally add functionality to static pages.
Many Content Management Systems (CMS) use PHP.
Many PHP libraries [4] available: Templates, XML parsers, compression, databases, etc.

PHP

1 Background

2 Language Basics

2.1 Quotes

2.2 Types

2.3 Super Globals

2.4 Execute This

3 Functions

3.1 Call By Reference

3.2 Default Values

3.3 Multiple Arguments

3.4 Function Scope

3.5 Functions are Objects

4 Arrays

4.1 Associative Arrays

4.2 Array Iteration

4.3 Manipulations

4.4 Filter

4.5 In Array

4.6 Sorting

4.7 Serialize

5 Objects

5.1 Class Variables

5.2 This

5.3 Access Control

5.4 Constructors and Destructors

5.5 Copying an Object

5.6 Comparisons

5.7 Static Class Variables

6 Forms

7 Cookies

8 Sessions

9 MySQL

10 Conclusion

URLs