03phpbldgblock

PHP

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THE BUILDING BLOCKS

Contents

Anatomy Literals Data Types Variables Constant


A PHP script is a web file with .php extension and is consisting of

text, HTML, and PHP instructions interspersed/intertwined throughout

the file.

The PHP instructions are contained within two php tags; <?php

…the opening tag & the closing tag.. ?>.

The content between these two tags is interpreted by the Zend

engine (PHP module/the interpreter) and converted to regular text &

HTML before being sent back to the requesting browser.

This way browser wont see any of the PHP content of PHP

scripting in the file it requested.

Consider the following exercise, and have a look at source code

on the browser .

Anatomy


<html>

<body>

<?php $string = ‘world’;

echo “<b1> Salam to the $string.<br />“ ;

?>

</body

</html>

Four different styles of tagging PHP:

1) XML style

<?php echo “salam world”; ?>

a default style (no configuration needed)

most preferred style

blend with other XML document

2) Short style

<? echo “salam world”; ?>

disabled by default

configuration needed in php.ini (short_open_tag= ‘on’)

the simplest tag style

follows SGML processing instructions style

interfere with XML document

Literals


Four different styles of tagging PHP:

3) script style < script language = “php”> echo “salam world !”; </script>

Enabled by default (no configuration needed)

the longest tag style

Follows executing Javascript and VBscript style

An alternative style if using other styles cause a

problem in HTML editor

4) ASP style

<% echo “salam world !”; %>

Configuration needed in php.ini (asp_tag = ‘on’)

Disabled by default

The ASP web developer friendly styles

Follows ASP processing instruction style

Interfere with XML document

Literals


Tagging comments in PHP:

i. Blocked comments : example –

/* a long paragraphed comment can be addressed and

exploited within this compound. PHP scripts rendered

non-executable within these symbols */

ii. Line comments:

// a one line comment is addressed like this.

// add another double slashes to add a next line comment

Literals


PHP supports four core data types:

1) Integers whole numbers and do not contain a decimal point;

integers can be expressed in decimal (base 10), octal (base 8),

and hexadecimal (base 16), and are either positive or negative

values.

e.g. 12345 integer, 0x456fff integer in base 16(hexadecimal), 0777

integer in base 8(octal)

2) Float (also called double or reals) fractional numbers such as

123.56 or –2.5. They must contain a decimal point or an exponent

specifier, such as 1.3e–2. The letter “e” can be either uppercase

or lower case.

e.g. 23.45 float, .234E–2 float in scientific notation, .234e+3 float

in scientific notation.

Data types



3) String a sequence of characters, either as a literal constant or

as some kind of variable. Some notes on string operations ! :

a) Single quotes treat all character equally e.g. $str = ‘$sign’

b) Double quotes DO NOT treat all characters equally. e.g.

$str =“another $str”;

c) String can contain escape sequences (a single character

preceded with backlash ‘\’). Backlash can be used for quoting

‘conflicting’ character. e.g. $str = ‘I can\’t help you !’;

Data types



3) String escape sequences (a single character preceded with

backlash ‘\’).

Other uses of escape sequences as follows

Data types



4) Boolean or boolean logic, is a subset of algebra used for creating

true/false statements. Boolean expressions use the operators AND, OR,

XOR, and NOT to compare values and return a true or false result. These

boolean operators are described in the following four examples:

x AND y - returns True if both x and y are true; returns False if either

x or y are false.

x OR y - returns True if either x or y, or both x and y are true; returns

False only if x and y are both false.

X OR y - returns True if only x or y is true; returns False if x and y are

both true or both false.

NOT x - returns True if x is false (or null); returns False if x is true.

Data types


http://www.techterms.com/definition/null

PHP also supports 4 other SPECIAL data types:

1) NULL

2) ARRAY

3) OBJECT

4) RESOURCES

Data types


Types of Variables in PHP

Predefined variables

User defined variables

Form variables related to names in an HTML form

Variables


Predefined variables

Variables


User Defined Variables = by value

Variables


Criteria : a) A variable must have a name

Variable name starts with a dollar sign ($), followed by a character

or a set of alphanumeric chars including underscore. e.g. $user,

$3int, $_fraction etc.

b) A variable must have value

A variable is complete as soon as a value is assigned to it. e.g.

$user = ‘ali’; or $3int = 321; or $_fraction = 2.17; or $_bool=

FALSE etc. A variable is complete as soon as a value is assigned

to it. e.g.

c) A variable must have type

A variable type goes by the data type it is initiated with. e.g. $user

= ‘ali’; //a string var or $3int = 321 //int variable; or $_fraction =

2.17; // float var or $_bool= FALSE etc.

d) A variable name is case sensitive

e.g. $var and $VAR are referring to two different variables.

Displaying variable

Variables


echo “parameter” - output one or more string and all

parameters. (void echo ( string $arg1 [, string $... ] ). It can take a

comma-separated list of string arguments

print “arg” - Outputs a string. (int print (string $arg).

Example:

$name = “Omar”; $state = “Selangor”;$salary = 10000;

echo $name, $state, $salary;

print $name;

print $name.$state.$salary;

echo $name.$state.$salary;

print “$name $state $salary <br/>”;

echo “$name $state $salary <br/>”;

String Concatenator

Variables


String or string variables can be concatenated using

i. Operator (‘.’) to left or to right sight of an argument.

ii. Operator (‘.=’) which appends the argument on the

right side to the argument on the left side.

Example: <?php

$a = ’Salam ’; $b = ‘World ’; $c=1000;

$d = $a . $b; // now $d contains “Salam World"

echo $b.$c; // display ‘World 0’

$a = "Hello ";

$a .= "World!"; // now $a contains "Hello World!"

?>

User Defined variables = by memory reference

Variables


References in PHP are a means to access the same

variable value by different memory references.

Example: <?php

$foo = ‘Salam'; //define $foo by assigning it with a string value ‘salam‘

$bar = 'World'; //define $foo by assigning it with a string value ‘world‘

$foo = $bar; //assigning $foo by value of $bar

$bar = ‘Salam’;

print $foo; // world

$foo = &$bar; // assigning both to each other’s memory references

$foo .= ‘ My World';

print $bar;// Salam My World

?>

Managing variables

Variables


Managing variables – examples

Variables


<?php $var = ‘ ‘; // This will evaluate to TRUE so the text will be printed. if (isset($var)) { echo "This var is set so I will print."; } // var_dump is used to dump content to the output // the return value of isset(). $a = "test"; $b = "anothertest"; var_dump(isset($a)); // TRUE var_dump(isset($a, $b)); // TRUE unset ($a); var_dump(isset($a)); // FALSE var_dump(isset($a, $b)); // FALSE $foo = NULL; var_dump(isset($foo)); // FALSE ?>

Variable variables (Dynamic variables)

Variables


A variable variable takes the value of a variable and

treats that as the name of a variable

Example: <?php

$a = ‘Salam'; // a variable name $a is assigned with a value

$$a = ‘ world’; // the value of $a i.e ‘salam’ is turned to be a variable

// name and it’s assigned with a string ‘world’

echo "$a ${$a}"; // output is ‘Salam world’

echo "$a $salam"; // produce exactly the same ‘Salam world’

?>

Form variables

Variables


For each HTML form parameter, PHP creates a global variable by

the same name and makes it available to your script.

Creating the same variable names in PHP file from the form variables

requires use of extract(parameter) function in PHP file.

Example HTML form syntaxes:

<input type=“text” name=“your_name”>

<input type=“text” name=“your_phone”>

PHP will create a variable called $your_name for a text field named

“your_name”

PHP will create a variable called $your_phone for a text field named

“your_phone”

Form variables - example

Variables


updateWarna.html

theUpdate.php

Constant


A constant is a value that, once set, cannot be

changed or unset during the execution of your

script.

It is global in scope.

Can be created using define() function

defines a named constant. Description : bool define ( string $name , mixed $value

[$case_insensitive = false ] )

Constant


Example :

<?php

define("CONSTANT", “Salam world.");

echo CONSTANT; // outputs “Salam world."

echo Constant; // outputs "Constant" and issues a notice.

define("GREETING", “Salam you all.", true);

echo GREETING; // outputs “Salam you all."

echo Greeting; // outputs “Salam you all.”

?>

Constant


Constant () function Return the value of the

constant indicated by name.

constant() is useful if you need to retrieve the

value of a constant, but do not know its name. i.e.

it is stored in a variable or returned by a function.

<?php

define("MAXSIZE", 100);

echo MAXSIZE; // or

echo constant("MAXSIZE"); // same thing as the previous line

?>

Constant


Built-in Constants

Constant


Magic Constants

PHP


THE BUILDING BLOCKS

Date post:	14-Apr-2017
Category:	Education
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