Php Chapter 1 Training

PHP Basics Orlando PHP Meetup Zend Certification Training January 2008

Anatomy of a Web Request

What happens when you request index.php?

Web server (Apache) loads handler, php application and provides URL and POST data, if any.

PHP:

Parse page to split code from html

Compile code

Execute code

Merges code output with html

Stream back to Apache, which forwards to the users browser.

PHP Syntax

Tags (Must be matched pairs)

<?php code ?> - Recommended

<? ?> - Frequently used, <?= ?> (auto echo)

<% %>, <script language=“php”> </script>

Whitespace

Inside script tags: Ignored

Just don’t break any <?php tags or function names.

Outside script tags: Sent to output stream exactly

Case Sensitive

$This != $this != $THIS

Comments

// Single line comment - Preferred

# Single line comment – Valid but deprecated

/* Multi-line comment */

/** * API Documentation Example * * @param string $bar */ function foo($bar) { }

Variables

All variables start with dollar sign: $

$scalar – Holds a single value

$array[$index] – Single element of an array

$object->method() – Object and method

$object->property – Object and property

Variable variables: $$variablename

$variablename = ‘size’;

$$variablename == $size

(Use sparingly, can drive mortal programmers insane)

Language Constructs

Code Blocks – Wrapped in {}

{ // Some comments f(); // a function call }

Statements terminated with semicolon.

Single or multiline:

echo(‘this is printed’ . ‘on a single ‘ . ‘line.’);

Data Types

Scalar Types

boolean - A value that can only either be false (value == 0 or value = ‘’ or value ==‘0’) or true (any other value)

int - A signed numeric integer value

Decimal: 1234567890

Octal: 01234567 (Leading zero)

Hex: 0x1234567890ABCDEF

float - A signed ﬂoating-point value

Decimal: 12345.6789

Exponential: 123.45e67 or 123.45E67

string - A collection of character or binary data

Data Types (2)

Compound Types

Array – An ordered hash of key => value pairs

Key evaluates to integer or string

Value may be any data type.

Object – Containers of data and code.

Special Types

Resource – Handle to a file, database or connection

NULL – A special value for an uninitialized variable

Data Type Conversion

Loosely typed

A single variable can contain different types over it’s lifespan

Mostly transparent, but can be forced

$var = (int) (‘123’ + ‘456’) == 123456

$var = (int) ‘123’ + ‘456’ == 579 (Early bind)

Cannot convert TO a resource or class.

When converting to a boolean:

false == 0, ‘0’, ‘’, null, unset()

true == (! false) (Caution: ’00’ or ‘ ‘ == true)

Variable Naming

Must start with a dollar sign: $

Then a character (a-zA-z) or underscore

May contain numbers (not first character)

Except variable variables

$var = ‘123’

$$var = ‘value’

echo ${‘123’}; //outputs ‘value’

No punctuation or special characters

Valid: $value, $value123, $_val

Not Valid: $1value, $value.two, $value@home

Variable Scope

Function

Defined when first referenced (var) or assigned to.

Not inherited from the call stack.

Disposed when function exits

Global

Defined outside a function

Inherit into a function with global() or $GLOBALS[‘varname’]

Limit use to improve maintainability

Class

Class properties are visible within the class via $this->varname

Constants

define(‘CONSTANT’, ‘scalarvalue’);

echo CONSTANT; //No $ or single quote

Immutable, scopeless, ONLY scalar values (int, float, boolean, string)

Operators 1

Assignment Operators

assigning data to variables ($a = 1; $b = $c = 2;)

Value: $b = $a Reference: $b = &$a; (makes copy)

Arithmetic Operators

performing basic math functions ($a = $b + $c;)

String Operators

joining two or more strings ($a = ‘abc’ . ‘def’;)

Comparison Operators

comparing two pieces of data ($boolean = $a or $b;)

Logical Operators

performing logical operations on Boolean values

Operators 2

Bitwise Operators

Manipulating bits using boolean math ($a = 2 & 4;)

Error Control Operators

Suppressing errors ($handle = @fopen();)

Execution Operators

Executing system commands ($a = `ls –la`;)

Incrementing/Decrementing Operators

Inc. and dec. numerical values ($a += 1; $a++; ++$a;)

Type Operators

Identifying Objects

Operator Precedence & Associativity instanceof non-associative , left or left xor left and left = += -= *= /= .= %= &= |= ˆ= <<= >>= right ? : left || left && left | left * left & left == != === !== non-associative < <= > >= non-associative << >> left + - . left * / % left ! Right ˜ - (int) (float) (string) (array) (object) @ non-associative ++ - non-associative [ left Operator Associativity

Control Structures

If – Then – Else

if (expression1) { // True expressions } elseif (expression2) { // Optional space between else and if } else { // Nothing else matches }

($a == $b) ? $truevalue : $falsevalue;

Switch statement

Does not need to evaluate on each comparison

$a = 0; switch ($a) { // In this case, $a is the expression case true: // Compare to true // Evaluates to false break; case 0: // Compare to 0 // Evaluates to true break; default: // Will only be executed if no other conditions are met break; }

Iteration Constructs

While (pre-comparison)

$i = 0; while ($i < 10) { echo $i . PHP_EOL; $i++; }

Do (post comparison)

$i = 0; do { echo $i . PHP_EOL; $i++; } while ($i < 10);

for() and foreach()

for(init ; compare ; increment) {}

for ($i = 0; $i < 10;$i++) { echo $i . PHP_EOL; }

foreach ($array as $element)

$arr = array (‘one’, ‘two’, ‘three’); foreach ($arr as $item){ echo $item . PHP_EOL; }

foreach ($assoc_array as $key => $item)

$arr = array (‘one’ => ‘uno’, ‘two’ => ‘dos’); foreach ($arr as $english => $spanish) { echo “$english means $spanish ”; }

Breaking Out: break [n]

Exits the current loop ( for, foreach, while, do-while or switch but NOT if) and optionally parents

$i = 0; while (true) { if ($i == 10) { break; } echo $i . PHP_EOL; $i++; }

for ($i = 0; $i < 10; $i++) { for ($j = 0; $j < 3; $j++) { if (($j + $i) % 5 == 0) { break 2; // Exit from this loop and the next one. } } } //break continues here

Continue

Skips rest of loop and restarts

for ($i = 0; $i < 10; $i++) { if ($i > 3 && $i < 6) { continue; } echo $i . PHP_EOL; }

Can also take an optional parameter to restart optional parents.

Errors and Error Management

Types of errors:

Compile-time errors

Errors detected by the parser while it is compiling a script. Cannot be trapped from within the script itself.

Fatal errors

Errors that halt the execution of a script. Cannot be trapped.

Recoverable errors

Errors that represent signiﬁcant failures, but can still be handled in a safe way.

Warnings

Recoverable errors that indicate a run-time fault. Do not halt the execution of the script.

Notices

Indicate that an error condition occurred, but is not necessarily signiﬁcant. Do not halt the execution of the script.

Error Reporting

Set via INI configurations

error_reporting=E_ALL & ~E_NOTICE

From code: error_reporting(E_ALL & ~E_NOTICE)

display_errors = on #Show in browser

log_errors = on # Write to log file or web server log

Handling Errors

Global error handling function

$oldErrorHandler = ’’; //Stores name of old function function myErrorHandler($errNo, $errStr, $errFile, $errLine, $errContext) { global $oldErrorHandler; logToFile("Error $errStr in $errFile at line $errLine"); // Call the old error handler if ($oldErrorHandler) { $oldErrorHandler ($errNo, $errStr, $errFile, $errLine, $errContext); } } //Set up a new error handler function, returns the old handler function name $oldErrorHandler = set_error_handler(’myErrorHandler’);