Lazy Talk: PHP

Apache is a web server

Web server (or HTTP server) delivers web pages on the request to clients. This means delivery of HTML documents and any additional content that may be included by a document, such as images, style sheets and JavaScripts.

A client (web browser) initiates communication by making a request for a specific resource using HTTP and the server responds with the content of that resource or an error message if unable to do so.

HTTP (Hypertext Transfer Protocol)

HTTP functions as a request-response protocol in the client-server computing model.

HTML HyperText Markup Language

Create a file named hello.php and put it in your web server's root directory (DOCUMENT_ROOT)

hello.php

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">

<html><head><title>Example</title></head><body>
<?php echo "Hi, I'm a PHP script!";?>
</body></html>

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<?php phpinfo(); ?>

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<?php echo $_SERVER['HTTP_USER_AGENT']; ?>

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<?php
if (strpos($_SERVER['HTTP_USER_AGENT'], 'MSIE') !== FALSE) {

echo 'You are using Internet Explorer.<br/>';
}?>

form.html

</form>

action.php

<?php echo htmlspecialchars($_POST['name']); ?>.
You are <?php echo (int)$_POST['age']; ?> years old.

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// This is a one-line c++ style comment
/* This is a multi line comment
yet another line of comment */
# This is a one-line shell-style comment
--------------------------

$a_bool = TRUE;   // a boolean
$a_str  = "foo";  // a string
$a_str2 = 'foo';  // a string
$an_int = 12;     // an integer

echo gettype($a_bool);//boolean
echo gettype($a_str);//string
if (is_int($an_int))  $an_int += 4;
if (is_string($a_bool)) echo "String: $a_bool";
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if ($action == "show_version")

echo "The version is 1.23";
if ($show_separators) echo "<hr>\n";

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$a = 1234; // decimal number
$a = -123; // a negative number
$a = 0123; // octal number (equivalent to 83 decimal)$a = 0x1A; // hexadecimal number (equivalent to 26 decimal)

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$a = 1.234; $b = 1.2e3; $c = 7E-10;
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echo 'string';
echo 'string

with newlines ';
// Outputs: Arnold once said: "I'll be back"
echo ' Arnold once said: "I\'ll be back" ';
echo ' \\ '; // \
// Outputs: You deleted C:\*.*?
echo ' You deleted C:\*.*? ';
// Outputs: This will not expand: \n a newline
echo ' This will not expand: \n a newline ';
// Outputs: Variables do not $expand $either
echo ' Variables do not $expand $either ';
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$str = <<<EOD
Example of string
spanning multiple lines
using heredoc syntax.
EOD;

/* More complex example, with variables. */
class foo { var $foo;   var $bar;
    function foo(){ $this->foo = 'Foo';
        $this->bar = array('Bar1', 'Bar2', 'Bar3'); } }

$foo = new foo();   $name = 'MyName';

echo <<<EOT
My name is "$name". I am printing some $foo->foo.
Now, I am printing some {$foo->bar[1]}.
This should print a capital 'A': \x41
EOT;
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$arr = array("foo" => "bar", 12 => true);
echo $arr["foo"]; // bar
echo $arr[12]; // 1
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class foo { function do_foo() {echo "Doing foo.";} }
$bar = new foo; $bar->do_foo();
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$foo = 'Bob';// Assign the value 'Bob' to $foo
$bar = &$foo; // Reference $foo via $bar.
$bar = "My name is $bar"; // Alter $bar...
echo $bar; echo $foo; // $foo is altered too.
--------------------------

$a = 1;   $b = 2;
function Sum(){  global $a, $b;   $b = $a + $b;  }
Sum();   echo $b;
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$a = 1; $b = 2;

function Sum(){

$GLOBALS['b'] = $GLOBALS['a'] + $GLOBALS['b'];}

Sum(); echo $b;

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var_dump($a); //Dumps information about a variable

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print_r ($a); //Prints human-readable information about a variable

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$arr = array("somearray" => array(6 => 5, 13 => 9, "a" => 42));

echo $arr["somearray"][6]; // 5

echo $arr["somearray"][13]; // 9

echo $arr["somearray"]["a"]; // 42

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// This array is the same as ...

array(5 => 43, 32, 56, "b" => 12);

// ...this array

array(5 => 43, 6 => 32, 7 => 56, "b" => 12);

--------------------------

$arr = array(5 => 1, 12 => 2);

$arr[] = 56; // This is the same as $arr[13] = 56;

// at this point of the script

$arr["x"] = 42; // This adds a new element to

// the array with key "x"

unset($arr[5]); // This removes the element from the array

unset($arr); // This deletes the whole array

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$array = array(1, 2, 3, 4, 5);// Create a simple array.

// Now delete every item, but leave the array itself intact:

foreach ($array as $i => $value) { unset($array[$i]);}

// Append an item (note that the new key is 5, instead of 0).

$array[] = 6;

$array = array_values($array);// Re-index:

$array[] = 7;

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$a = array(1 => 'one', 2 => 'two', 3 => 'three');

unset($a[2]);

/* will produce an array that would have been defined as

$a = array(1 => 'one', 3 => 'three');

and NOT

$a = array(1 => 'one', 2 =>'three');

$b = array_values($a);

// Now $b is array(0 => 'one', 1 =>'three')

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$obj = (object) 'ciao';

echo $obj->scalar; // outputs 'ciao'

--------------------------

$var = NULL;

--------------------------

$a = 'car'; // $a is a string

$a[0] = 'b'; // $a is still a string

echo $a; // bar

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$a = 1; include 'b.inc'; //$a variable will be available within the included b.inc script

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A static variable exists only in a local function scope, but it does not lose its value when program execution leaves this scope

function test() { static $a = 0; echo $a; $a++; }

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$a = 'hello';

$$a = 'world'; // $hello = 'world';

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Name: <input type="text" name="username" /><br />

Email: <input type="text" name="email" /><br />

</form>

<?php

// Available since PHP 4.1.0

echo $_POST['username'];

echo $_REQUEST['username'];

import_request_variables('p', 'p_');

echo $p_username;

// As of PHP 5.0.0, these long predefined variables can be disabled with the register_long_arrays directive.

echo $HTTP_POST_VARS['username'];

// Available if the PHP directive register_globals = on. As of PHP 4.2.0 the default value of register_globals = off. Using/relying on this method is not preferred.

echo $username;

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// constants

define("FOO", "something");

const CONSTANT = 'Hello World';

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$a = 3 * 3 % 5; // (3 * 3) % 5 = 4

$a = true ? 0 : true ? 1 : 2; // (true ? 0 : true) ? 1 : 2 = 2

$a = 1; $b = 2;

$a = $b += 3; // $a = ($b += 3) -> $a = 5, $b = 5

// mixing ++ and + produces undefined behavior

$a = 1;

echo ++$a + $a++; // may print 4 or 5

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$a % $b; //Modulus

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$a == $b //TRUE if $a is equal to $b after type juggling.

$a === $b //TRUE if $a is equal to $b, and they are of the same type.

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PHP supports one error control operator: the at sign (@). When prepended to an expression in PHP, any error messages that might be generated by that expression will be ignored.

/* Intentional file error */

$my_file = @file ('non_existent_file') or

die ("Failed opening file: error was '$php_errormsg'");

// this works for any expression, not just functions:

$value = @$cache[$key];

// will not issue a notice if the index $key doesn't exist.

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// Get a file into an array. In this example we'll go through HTTP to get the HTML source of a URL.

$lines = file('http://www.example.com/');

// Loop through our array, show HTML source as HTML source; and line numbers too.

foreach ($lines as $line_num => $line)

{ echo "Line #<b>{$line_num}</b> : " . htmlspecialchars($line) . "<br />\n";}

// Another example, let's get a web page into a string. See also file_get_contents().

$html = implode('', file('http://www.example.com/'));

// Using the optional flags parameter since PHP 5

$trimmed = file('somefile.txt', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);

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$output = `ls -al`;//execute the contents of the backticks as a shell command

echo "<pre>$output</pre>";

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UNION OF ARRAYS

$a = array("a" => "apple", "b" => "banana");

$b = array("a" => "pear", "b" => "strawberry", "c" => "cherry");

$c = $a + $b; // Union of $a and $b

//$c = array("a" => "apple", "b" => "banana", "c" => "cherry");

for keys that exist in both arrays, the elements from the left-hand array will be used, and the matching elements from the right-hand array will be ignored.

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string get_class ([ object $object = NULL ] )

Returns the name of the class of an object

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if ($a > $b) echo "a is bigger than b";

elseif ($a == $b) echo "a is equal to b";

else echo "a is smaller than b";

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foreach (array_expression as $value)

statement

foreach (array_expression as $key => $value)

statement

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$arr = array("one", "two", "three");

reset($arr);

while (list($key, $value) = each($arr))

echo "Key: $key; Value: $value<br />\n";

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

echo "Key: $key; Value: $value<br />\n";

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switch ($i) {

case 0: echo "i equals 0"; break;

case 1: echo "i equals 1"; break;

case 2: echo "i equals 2"; break; }

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function add_some_extra(&$string)

{ $string .= 'and something extra.'; }

$str = 'This is a string, '; add_some_extra($str);

echo $str; // outputs 'This is a string, and something extra.'

function makecoffee($type = "cappuccino")

{ return "Making a cup of $type.\n"; }

echo makecoffee();//Making a cup of cappuccino.

echo makecoffee(null);//Making a cup of .

echo makecoffee("espresso");//Making a cup of espresso.

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function makecoffee($types = array("cappuccino"), $coffeeMaker = NULL)

{ $device = is_null($coffeeMaker) ? "hands" : $coffeeMaker;

return "Making a cup of " . join(", ", $types) . " with $device.\n" ; }

echo makecoffee();

echo makecoffee(array("cappuccino", "lavazza"), "teapot");

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join() is an alias of implode()

$array = array('lastname', 'email', 'phone');

$comma_separated = implode(",", $array);

echo $comma_separated; // lastname,email,phone

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function square($num) { return $num * $num; }

echo square(4); // outputs '16'.

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function small_numbers() { return array (0, 1, 2); }

list ($zero, $one, $two) = small_numbers();

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$info = array('coffee', 'brown', 'caffeine');

list($drink, $color, $power) = $info;

list($drink, , $power) = $info;

list( , , $power) = $info;

// list() doesn't work with strings

list($bar) = "abcde";

var_dump($bar); // NULL

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$result = mysql_query("SELECT id, name, salary FROM employees", $conn);

while (list($id, $name, $salary) = mysql_fetch_row($result)) { echo " <tr> \n " .

" <td> <a href = \"info.php?id=$id\" > $name </a> </td> \n" .

" <td> $salary </td> \n" .

" </tr> \n "; }

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list($a, list($b, $c)) = array(1, array(2, 3));

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function foo() { echo "In foo()"; }

function bar($arg = '')

{ echo "In bar(); argument was '$arg'"; }

function echoit($string) { echo $string; }

$func = 'foo'; $func(); // This calls foo()

$func = 'bar'; $func('test'); // This calls bar()

$func = 'echoit'; $func('test'); // This calls echoit()

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class Foo {

function Variable() { $name = 'Bar';

$this->$name(); // This calls the Bar() method }

function Bar() { echo "This is Bar"; }

} //class Foo

$foo = new Foo();

$funcname = "Variable";

$foo->$funcname(); // This calls $foo->Variable()

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class Foo{ static $variable = 'static property';

static function Variable() { echo 'Method Variable called';} }

echo Foo::$variable; // This prints 'static property'. It does need a $variable in this scope.

$variable = "Variable";

Foo::$variable(); // This calls $foo->Variable() reading $variable in this scope.

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$greet = function($name){ printf("Hello %s\r\n", $name); };

$greet('World'); $greet('PHP');

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class SimpleClass {

// property

public $var = 'a default value';

// method

public function displayVar()

{ echo $this->var;} } //class

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class A{

function foo(){

if (isset($this)) {

echo '$this is defined (';

echo get_class($this);

echo ")\n"; }

else echo "\$this is not defined.\n";

}

class B{

function bar(){

// Note: the next line will issue a warning if E_STRICT is enabled.

A::foo();} }

$a = new A(); $a->foo();

// Note: the next line will issue a warning if E_STRICT is enabled.

A::foo(); $b = new B(); $b->bar();

// Note: the next line will issue a warning if E_STRICT is enabled.

B::bar();

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$instance = new SimpleClass();

// This can also be done with a variable:

$className = 'Foo';

$instance = new $className(); // Foo()

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Lazy Talk

Wednesday, February 22, 2012

PHP

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