Download It

Quick and Dirty Intro to PHP

By David Choffnes(content shamelessly ripped from the manual)

What is PHP?

• PHP (recursive acronym for "PHP: Hypertext Preprocessor") is a widely-used Open Source general-purpose scripting language that is especially suited for Web development and can be embedded into HTML.– Write an HTML script with some embedded

code to do something– Code is executed on the server.

What is PHP?

• An example:• Example 1-1. An introductory example

<title>Example</title></head><body>

<?php echo "Hi, I’m a PHP script!";?>

</body></html>

Ridiculous DB support (and more)

• Writing a database-enabled web page is incredibly simple. The following databases are currentlysupported:– Adabas D, Ingres, Oracle (OCI7 and OCI8), dBase, InterBase,

Ovrimos, Empress, FrontBase, PostgreSQL, FilePro (read-only), mSQL, Solid Hyperwave, Direct MS-SQL, Sybase, IBM DB2, MySQL, Velocis, Informix, ODBC, Unix dbm

• DBX database abstraction extension – allows you to transparently use any database

• Supports ODBC, the Open Database Connection standard,

• Support for talking to other services using protocols such as LDAP, IMAP, SNMP, NNTP, POP3, HTTP, COM (on Windows) and countless others.

Basic syntax

• Escaping from HTML– Example 5-1. Ways of escaping from HTML1. <? echo ("this is the simplest, an SGML processing instruction\n"); ?>

<?= expression ?> This is a shortcut for "<? echo expression ?>"

2. <?php echo("if you want to serve XHTML or XML documents, do like this\n"); ?>

3. <script language="php"> echo ("some editors (like FrontPage) don’t like processing instructions");

</script>4. <% echo ("You may optionally use ASP-style tags"); %>

<%= $variable; # This is a shortcut for "<% echo . . ." %>

Basic Syntax

• Example 5-2. Advanced escaping<?phpif ($expression) {?><strong>This is true.</strong><?php

} else {?><strong>This is false.</strong><?php

Instruction Separation

• Instructions are separated the same as in C or Perl - terminate each statement with a semicolon.

• The closing tag (?>) also implies the end of the statement, so the following are equivalent:

<?phpecho "This is a test";?><?php echo "This is a test" ?>

Comments

• PHP supports C, C++ and Unix shell style comments<?phpecho "This is a test"; // This is a one-line c++ style comment

/* This is a multi line commentyet another line of comment */echo "This is yet another test";echo "One Final Test"; # This is shell-style style comment

• PHP supports eight primitive types.– Four scalar types:

• boolean• integer• floating-point number (float)• string

– Two compound types:• array• object

– And finally two special types:• resource• NULL

Scalars

• Very simple:– $foo = true; (boolean)– $foo = 20; (integer)– $foo = 3.1415; (float)

Strings

• A string literal can be specified in three different ways.– single quoted

• Variables not expanded

– double quoted• $foo = 20;• echo “The value of foo is $foo”;

Strings

– heredoc syntaxExample 6-2. Here doc string quoting example<?php$str = <<<EOD

Example of stringspanning multiple linesusing heredoc syntax.

EOD;?>

Arrays

• Specifying with array()– An array can be created by the array() language-

construct. It takes a certain number of comma-separated key => value pairs.

– A key is either a nonnegative integer or a string. If a key is the standard representation of a non-negative integer, it will be interpreted as such (i.e. ’8’ will be interpreted as 8, while ’08’ will be interpreted as ’08’).

– A value can be anything.– If you omit a key, the maximum of the integer-indices

is taken, and the new key will be that maximum +1. If no integer-indices exist yet, the key will be 0 (zero). If you specify a key that already has a value assigned to it, that value will be overwritten.

Arrays

array( [key =>] value, ...)// key is either string or nonnegative integer// value can be anything

Creating/modifying with square-bracket syntax– You can also modify an existing array, by explicitly setting

values.– This is done by assigning values to the array while specifying the

key in brackets. You can also omit the key, add an empty pair of brackets ("[]") to the variable-name in that case.

Arrays

$arr[key] = value;$arr[] = value;// key is either string or nonnegative integer

// value can be anything

Objects

• Object Initialization– To initialize an object, you use the new statement to

instantiate the object to a variable.<?phpclass foo{

function do_foo(){

echo "Doing foo.";}

}$bar = new foo;$bar->do_foo();

• The special NULL value represents that a variable has no value. NULL is the only possible value of type NULL.

Type Juggling

• PHP does not require (or support) explicit type definition in variable declaration;

• A variable’s type is determined by the context in which that variable is used. – If you assign a string value to variable var, var

becomes a string. If you then assign an integer value to var, it becomes an integer.

• Operators on multiple types do NOT change the types of the operands themselves; the only change is in how the operands are evaluated.

Type Juggling

• Example$foo = "0"; // $foo is string (ASCII 48)

$foo += 2; // $foo is now an integer (2)

$foo = $foo + 1.3; // $foo is now a float (3.3)

$foo = 5 + "10 Little Piggies"; // $foo is integer (15)

$foo = 5 + "10 Small Pigs"; // $foo is integer (15)

Variable Basics

• Variables in PHP are represented by a dollar sign followed by the name of the variable.

• Variable name is case-sensitive.• Variable names follow the same rules as other

labels in PHP. – A valid variable name

• starts with a letter or underscore• Followed by any number of letters, numbers, or underscores. • As a regular expression, it would be expressed thus: ’[a-zA-

Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*’

Variables

• Example$var = "Bob";

$Var = "Joe";

echo "$var, $Var"; // outputs "Bob, Joe"

$4site = ’not yet’; // invalid; starts with a number

$_4site = ’not yet’; // valid; starts with an underscore

$täyte = ’mansikka’; // valid; ’ä’ is ASCII 228.

References

• Example<?php

$foo = ’Bob’; // Assign the value ’Bob’ to $foo

$bar = &$foo; // Reference $foo via $bar.

$bar = "My name is $bar"; // Alter $bar...

echo $foo; // $foo is altered too.

echo $bar;

PHP Variables• $argv

– Array of arguments passed to the script. • $argc

– Contains the number of command line parameters passed to the script (if run on the command line).

• $PHP_SELF– The filename of the currently executing script, relative to the document root.

• $HTTP_COOKIE_VARS– An associative array of variables passed to the current script via HTTP cookies.

• $_COOKIE– An associative array of variables passed to the current script via HTTP cookies.

• $HTTP_GET_VARS– An associative array of variables passed to the current script via the HTTP GET

method.

PHP Variables

• $_GET– An associative array of variables passed to the current script via the

HTTP GET method.• $HTTP_POST_VARS

– An associative array of variables passed to the current script via the HTTP POST method.

• $_POST– An associative array of variables passed to the current script via the

HTTP POST method.• $HTTP_POST_FILES

– An associative array of variables containing information about files uploaded via the HTTP POST method.

• $_FILES– An associative array of variables containing information about files

uploaded via the HTTP POST method

PHP Variables

• $HTTP_ENV_VARS– An associative array of variables passed to the

current script via the parent environment.• $_ENV

– An associative array of variables passed to the current script via the parent environment.

• $HTTP_SERVER_VARS– An associative array of variables passed to the

current script from the HTTP server. • $_SERVER

– An associative array of variables passed to the current script from the HTTP server.

PHP Variables

• $HTTP_SESSION_VARS– An associative array of session variables passed to

the current script.

• $_SESSION– An associative array of session variables passed to

the current script.

• $_REQUEST– An associative array merged from the GET, POST,

and Cookie variables. In other words - all the information that is coming from the user, and that from a security point of view, cannot be trusted.

• Variables declared outside of functions, classes are global to the script, outside of function blocks

• Unlike C! Global variables are not automatically available to functions

• Example:$a = 1; /* global scope */function Test(){echo $a; /* reference to local scope variable */

}Test();

Variable Scope

• Access to global variables inside functions– Explicitly declare variable as global

global $a, $b;– Use the $GLOBALS array

$foo = $GLOBALS[“a”]

Variable Variables(aka, Dave blows your mind)

• A variable variable takes the value of a variable and treats that as the name of a variable. In the above$a = "hello";$$a = "world";

• Two variables have been defined and stored in the PHP symbol tree: – $a with contents "hello" – $hello with contents "world“

echo "$a ${$a}";produces the exact same output as:echo "$a $hello";

i.e. they both produce: hello world.

HTML Forms (GET and POST)

• When a form is submitted to a PHP script, any variables from that form will be automatically made available to the script by PHP.

• Located in the associative arrays $HTTP_POST_VARS, $HTTP_GET_VARS, and/or

• $HTTP_POST_FILES, according to the source of the variable in question.

• Example 7-1. Simple form variable<form action="foo.php" method="post">Name: <input type="text" name="username"><br><input type="submit"></form>

• When the above form is submitted, the value from the text input will be available in $HTTP_POST_VARS[’username’].

More Complex HTML Forms

• Example 7-2. More complex form variables<form action="array.php" method="post">Name: <input type="text" name="personal[name]"><br>

Email: <input type="text" name="personal[email]"><br>

Beer: <br><select multiple name="beer[]"><option value="warthog">Warthog<option value="guinness">Guinness<option value="stuttgarter">Stuttgarter Schwabenbräu

</select><input type="submit"></form>

Cookies!

• Set cookies using the setcookie() function.– Cookies are part of the HTTP header, so the

SetCookie function must be called before any output is sent to the browser.

• Any cookies sent to you from the client will automatically be turned into a PHP variable just like GET and POST method data.

• If you wish to assign multiple values to a single cookie, just add [] to the cookie name. – For example:setcookie("MyCookie[]", "Testing", time()+3600);

Operators• Pretty much all of the operators as in

C++/Java/…• String comparison uses “==“

TRUE if $a is equal to $b, and they

Are of the same type

Identical$a === $b

TRUE if $a is equal to $b.Equal$a == $b

ResultNameExample

Control structures

• If, then, else, elseif, while, foreach, do…while, for, break, continue, switch, case, return

• Supports backticks like Perl

Other stuff

• require(/path/to/file.php)– Includes and evaluates the specified file

• include(...)– Same thing

• include_once(...)– Makes sure same file is not included multiple

User-defined functions

• A function may be defined using syntax such as the following:function foo ($arg_1, $arg_2, ..., $arg_n)

echo "Example function.\n";

return $retval;

Variable functions

• Example 12-1. Variable function example<?php

function foo(){

echo "In foo()<br>\n";}function bar($arg = ”){

echo "In bar(); argument was ’$arg’.<br>\n";}$func = ’foo’;$func();$func = ’bar’;$func(’test’);

Download It

value of foo

value key

string value

nonnegative integer

variable var

value pairs

separated key

new key

Documents

Download It