[Zend PHP5 Cerification] Lectures -- 1. PHP Basics, PHP Functions, Arrays

PHPBasics

PHPBasics refers to a number of things that

arelikely already second nature to you:

–Syntax

–Operators

–Variables

–Constants

–Control Structures

• LanguageConstructs and Functions

 

 

 

 

Magicconstants
__LINE__   The current linenumber of the file.
__FILE__   The full path andfilename of the file. If used inside an include, the name of theincluded file is returned. Since PHP 4.0.2, __FILE__always contains an absolute path whereas in older versions itcontained relative path under some circumstances.
__FUNCTION__   The function name.(Added in PHP 4.3.0) As of PHP 5 this constant returns the functionname as it was declared (case-sensitive). In PHP 4 its value isalways lowercased.
__CLASS__   The class name. (Addedin PHP 4.3.0) As of PHP 5 this constant returns the class name as itwas declared (case-sensitive). In PHP 4 its value is alwayslowercased.
__METHOD__   The class method name.(Added in PHP 5.0.0) The method name is returned as it was declared(case-sensitive).

 

PHPlanguage construct

The "exact"  definition for "LanguageConstruct".

It's kind of like the "core languagedefinition" of things such as: if (...) while (...) <?php and?> and so on In PHP, a handful of common things that manybeginners *THINK* are functions are actually Language Constructs:require include echo isset I belive most of them are documented assuch in the manual now. Language Construct roughly corresponds to the"grammar" of the language, if you will.

Thismeans that they are integral part of the language, just like 'if', orany operator +, *, etc, though they look pretty much like functions.It means that though syntactically they look a functions and in themanual they are listed under functions, this is only to make themeasy to use, understand and locate in the documentation. That is whycertain rules for functions can be relaxed, such as requiringparenthesis around its arguments, which are not actually needed butare there so that they have the same look as regular functions.

 

PHP Tags

Long tags: <?php … ?>

Script syle tags:

<script language = “php”> …</script>

Short tags: short_open_tag directive inphp.ini

<? …?> (<? echo $vars ?>;<?= $vars ?>)

ASP style tags: asp_tags directive inphp.ini

<% … %> (<% echo $vars %>;<%= $vars %>)

 

Except the long tags, other tags are notpreferred.

 

Exam questions:

.When you should not use short tags? When usephp with XML.

What kind of errors occurred due to the “shorttags” problem?

A. output javascript source code;

B. Parse error: syntax error,unexpected $end in

 

Use the long or regular PHP tags to ensureyour application will be portable across multiple servers regardlessof configuration options.

 

 

Comments

// single line comment

# single line comment

/*

Multi-line comment

*/

.PHPdoc comment style

 

Single line comments are ended by either thenewline character or a closing PHP tag, so a single like comment like

//This tag ?> can end PHP code

Can have unintended output

 

Variables

PHPis loosely typed.

Scalar:Boolean, string, integer, float

Compound:array, object

Special:resource, null

 

ScalarTypes

 

Strings

Natively within PHP each character is represented by asingle byte, as such PHP has no native support for multi-bytecharacter sets (like Unicode)

• This changeswith PHP6.

There is no PHP imposed limit on the length of the strings youcan use.

‘’ The single quote or string literal, characters within singlequotes will be recorded as is, without variable or escape sequencesinterpreted and replaced.

“” The double quotes, variables and escape sequnces will beinterpreted and replaced

<<<– Heredoc

Theheredoc syntax functions in a similar manner to double quotes, but isdesigned to span multiple lines, and allow for the use of quoteswithout escaping.

$greeting= <<<GREETING

Shesaid "That is $name's" dog!

Whilerunning towards the thief

GREETING;

 

Also,the identifier used must follow the same naming rules as any otherlabel in PHP: it must contain only alphanumeric characters andunderscores, and must start with a non-digit character or underscore.

 

Itis very important to note that the line with the closing identifiercontains no other characters, except possibly a semicolon (;). Thatmeans especially that the identifier may not be indented, and theremay not be any spaces or tabs after or before the semicolon. It'salso important to realize that the first character before the closingidentifier must be a newline as defined by your operating system.This is \r on Macintosh for example. Closing delimiter (possiblyfollowed by a semicolon) must be followed by a newline too.

 

Itis not allowed to use heredoc syntax in initializing class members.Use other string syntaxes instead.

 

Integer

0

0x

Maximum size of an integer is platformdependent, a maximum of ~2Billion is common.

 

Float (double)

Floats, or doubles, can be used to representreally

large or really small values. Floats can beentered

via several syntaxes

$a = 1.234; //Standard decimal notation

$b = 1.2e3; //Scientific notation (1200)

$c = 7E-10;

//Scientific notation (0.0000000007)

 The size of a float is platform-dependent,although a

maximum of ~1.8e308 with a precision

 

 

I encountered a questions on the numbernotation conversion. But is relative easy. By default, php is outdecimal numbers.

 

 

Boolean

True, false, 0, 1… case-insensitive

 

 

CompoundTypes

Arrays

Arrays cancontain any combination of other variable types, even arrays orobjects.

More details onlater lectures.

 

Objects

Objects allowdata and methods to be combined into one cohesive structure.

More details onlater lectures.

 

SpecialTypes

Resource

Aresource is a special variable that represents some sort of operatingsystem resource, generally an open file or database connection.

Whilevariables of the type resource can be printed out, their onlysensible use is with the functions designed to work with them.

Null

Anull variable is special in that it has no value and no type.

Nullis not the same as the integer zero or an zero length string (whichwould have types)

 

 

 

Constants

Constants allowyou to create a special identifier that can not be changed oncecreated, this is done using the define() function. Constants can notbe changed once set.

define('username','bob');

 

VariableVariables

Variable Variables are bothuseful and confusing:

$a= 'name';

$$a= "Paul";

echo$name; //Paul

 

There are several situationsin which Variable

Variablescan be useful, but use them with care as

theycan easily confuse other programmers.

 

 

Operators

PHP supports a multitude of Operators:

–Assignment

–Logical

–Arithmetic

–String

–Comparison

–Bitwise

–Other

 

.AssignmentBy Value vs By Reference

PassObjects argument in PHP5.

 

UsingBitwise Operations: &(and), |(or), ^(XOR), ~(NOT)

>>(ShiftRight), <<(Shift Left), paddingwith 0s.

Whatis the output of:

– 1& 2

– 2& 7

– 15& 24

– 1| 2

– 16| 15

– 8^ 6

– 15^ 7

 

Whatis the output of (within the context of

our8 bit binary world):

–~254

– 4>> 2

– 1<< 2

– 5>> 2

–7<< 3

 

 

OtherOperators

@:Suppresses errors from the following expression

``backticks:Execute the contents as a shell command

(shortcutfor shell_exec()).

Instanceof:Returns true if the indicated variable is an instance of thedesignated class, one of it’s subclasses or a designated interface.

 

Instanceofis somewhat important, cause I encounter some exam questionsregarding this.

 

ini_set("ERROR_LEVEL",E_STRICT);

$a= @myFunction();

functionmyFunction($a)

{

array_merge(array(),"");

}

 

 

$ls= `ls`;

 

 

$a= new stdClass;

if($a instanceof stdClass) { ... }

if($a !instanceof stdClass) { ... }

//ParseError

 

ControlStructures

If

–Alternate * code morereadable.

–Short ($express)?$var1:$var2

Switch

While

do

For

–Continue

–break

Foreach

Functions

–Paramaters

 Optional

 Byref

 Byval

 Objects

 Variable functions

Objects

• Later!

 

if,while, do, for, foreach can have alternate syntax, replace the { and} with : and end(if, while, do etc). Check some WordPress theme filefor real world example.

 

 

$a= 0;

while($a++ < 10)

{

echo$a;

}

echo$a;

 

 

return

Returnends execution and returns control to the calling scope, functionsboth inside an included file (returning control to the calling file)and from inside a function/method (returning control to the callingcode).

 

Exit

Haltexecution of the script, can optionally return a message, or an exitstatus (0-255).

 

Arare exam questions:

 

End ascript in PHP5:
    __halt_compiler() ;
   die();
    exit();

 

Conclusion

PHP Tags, multiple types withdifferent use rules (which ones are on/off by default, which ones aguaranteed?)

PHP is loosely typed, but there istyping going onunderneath the hood

Some assumptions are made (octalformat)

Binary is a pain in the neck, but ithas its

uses

Control structures have formats otherthan

theones commonly uses

 

PHPFunctions

–Readability

–Maintainability

–Code separation

–Modularity

 

Functions– Scope

Ithink this should expanded to cover the features related to variablescope: Super Global, global variable, local variables, classmembers(public, private, protect, final etc), constant, static etc.

ButPHP free memory on the end of every page load, so even staticvariable can across separate http request; that’s why we needcookies and sessions.

 

 

global $id;

globals[‘id’];

 

Theexam has several questions will need you to clearly understand theFunction Scope. And pass value Byref and Byval.

 

variable-lengthargument lists

Youcan use variable-length argument lists even if you do specifyarguments in the

functionheader.

func_get_args,func_num_args, func_get_arg

 

 

Functions& Objects, Friends at last

 InPHP4 Objects were thrown around ByVal,this meant that you made copies without

eventhinking about it.

 InPHP5 Objects are always passed ByRefunless you explicitly clone it, keep that in

Mind.

 

Conclusion

They’reterribly useful

You have to remember how scope works

–Practice tracing

Objects fly around by reference now

Return statements can exist anywherewithin thefunction, you can even have several

Avoid situations where the samefunction mayreturn nothing, or something (Zend

Studio’sCode Analyzer tests for this)

 

Whathappens if a function is defined then the PHP scope ends, thenresumes again later with the remainder of the function.

 

Is“_” a valid function name?

 

PHPArrays

EnumeratedArrays, Associative Arrays (hashes), Multi Dimensional Arrays

 

$a =array(5=>"b", 7, 9, "23" => 'c', 'j');
$b= array(1, 2, 3, 'f', 'fred' => $a);
 How do I access thevalue:
– 7                                       //  $a[6];
– ‘c’                                      // $a["23"];
– ‘b’ through the array $b        // $b['fred'][5]
– ‘f’                                       // $b[3]

ArrayIteration:

Wheniterating through an array via foreach() keep in mind it operates ona copy of the array.

 

Usingthe internal array pointer doesn’t have this problem.

 

ArrayIteration

end() – Move pointer tolast element

key() - Retreives keyfrom current position

next() – Advances arraypointer one spot then

returnscurrent value

prev() – Rewinds thearray pointer one spot, then

returnsthe current value

reset() – Resets thearray pointer to the beginning of

thearray

each() – Returns the

 

Internalarray pointers can be reset, but don’t reset on their own.

 

Foreach()

InPHP 5 items can be iterated over by reference rather than simply byvalue.

foreach($arrayAS &$value) { … }

 

Thisis likely will be examed!

 

SomeArray functions:

 

.sort()
Thisfunction sorts an array. Elements will be arranged from lowest tohighest when this function has completed.
This function assignsnew keys for the elements in array. It will remove any existing keysyou may have assigned, rather than just reordering thekeys.
.Ksort()
Sorts an array by key, maintaining key todata correlations. This is useful mainly for associativearrays.
.asort()
Sort an array and maintain indexassociation

array_push() array_unshift()
array_pop()    array_shift()

 
Inassociative arrays strings are used to key the data, keys containingonly digits are cast to integers.

array_keys() &array_values()

bool array_walk ( array &$array, callback$funcname [, mixed $userdata] )
Applies the user-defined functionfuncname to each element of the array array. Typically, funcnametakes on two parameters. The array parameter's value being the first,and the key/index second. If the optional userdata parameter issupplied, it will be passed as the third parameter to the callbackfuncname.

array_change_key_case()
Returns an array withall keys from input lowercased or uppercased. Numbered indices areleft as is.

array_merge()
You can merge arrays usingarray_merge(), when different associative arrays have duplicate keys,the values in the rightmost array takeprecedence.

array_splice()
Cut out a chunk of anarray

array_merge_recursive()
merges the elements of one ormore arrays together so that the values of one are appended to theend of the previous one. It returns the resulting array.

Ifthe input arrays have the same string keys, then the values for thesekeys are merged together into an array, and this is done recursively,so that if one of the values is an array itself, the function willmerge it with a corresponding entry in another array too. If,however, the arrays have the same numeric key, the later value willnot overwrite the original value, but will be appended.