Php using variables-operators
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Transcript of Php using variables-operators
PHP Basic
Khem [email protected]
Part I: Understanding PHP Basics
Using Variables and Operators
PHP
Prepared by KhmerCourse
Storing Data in Variables
៚ Some simple rules for naming variables
៙ Be preceded with a dollar symbol $
៙ And begin with a letter or underscore _
៙ Optionally followed by more letters, numbers, or underscore
៙ Be not permitted
ៜ Punctuation: commas ,, quotation marks ?, or periods .
ៜ Spaces
៙ e.g.
ៜ $id, $_name and $query3: valid
ៜ $96, $day. and email: invalid
៚ Variable names are case-sensitive.
៙ e.g. $name and $Name refer to different variables.
3
Assigning Values to Variables
៚ $var = val;
៙ e.g. assigningValues2Variables.php<?php $language = "PHP"; ?>
<h1>Welcome <?php echo $language;
?></h1>
៚ Dynamic variable's name
៙ e.g. dynamicVariableName.php<?php
$clone = "real";// create a
value of${$clone} =echo $real;?>
new variable dynamically$clone"REAL";// output: REAL
at run time from the
Is it possible for a variable's name itself to be a variable?
៚ echo(): print the value of a variable
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Destroying Variables
៚ e.g. destroyingVariables.php<?php
$apple = "Apple";echo $apple; // output: Apple// unset()unset($apple);echo $apple; // error: Undefined
variable
$banana = "Banana";
echo $banana; //
// NULL value$banana = NULL;echo $banana; //?>
output: Banana
output: (nothing)
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Inspecting Variable Contents
៚ e.g. inspectingVariableContents.php<?php
$apple = "Apple"; $yr = 2011;
// var_dump()
var_dump($apple);var_dump($yr); //
// output: string(5)
output: int(2011)"Apple"
// print_r()
print_r($apple); // output: Apple
print_r($yr);
?>// output: 2011
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Understanding PHP’s Data Types
៚ Data type is the values assigned to a variable.
៚ Booleans
៙ 1 (true) or 0 (false)
៚ 2 numeric
៙ Floating-point values (a.k.a floats or doubles) are decimal or fractional numbers,
៙ While integers are round numbers. ៚ Non-numeric: String
៙ Be enclosed in single quotes (') or double quotes (")
៚ NULL (a special data type in PHP4)
៙ Represent empty variables; a variable of type NULL is a variable withoutany data.
A NULL value is not equivalent to an empty string "".
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Understanding PHP’s Data Types (cont.)
៚ e.g. hexadecimal_octal_scientificNotation.php<?php$dececho
= 8; // decimal$dec; // output: 8
$octecho
= 010; // octal$oct; // output: 8
$hexecho
= 0x5dc;$hex; //
// hexadecimaloutput: 1500
// scientific notation$sn1$sn2echo?>
= 6.9e+2;= 6.9e-2;$sn1." ".$sn2; // output: 690 0.069
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Setting and Checking Variable Data Types
៚ e.g. setting_CheckingVariableDataTypes.php<?php
$apple = "Apple";echo gettype($apple); // output: string
$yr = 2011;echo gettype($yr); //
output: integer
$valid = true;echo gettype($valid); // output : boolean
echo gettype($banana); // output: NULLvariable)
(error: Undefined
$empty = NULL;echo gettype($empty); // output: NULL?>
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Setting and Checking Variable Data Types (cont.)
៚ e.g. casting.php<?php
$f_speed =
$i_speed =// output:
36.9; // floating-point
(integer)
36.9$f_speed; // cast to integer
echo $f_speed;
// output: 36echo
?>$i_speed;;
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Data Type Checking Functions
Function Purpose
is_bool Test if holding a Boolean value
is_numeric Test if holding a numeric value
is_int Test if holding an integer value
is_float Test if holding a float value
is_string Test if holding a string value
is_null Test if holding a NULL value
is_array Test if being an array
is_object Test if being an object
Using Constants
៚ define(CONST, val);
៚ Constant names follows the same rules as variable names but not the $
៚ e.g. usingConstants.php<?php
define("APPLE", "Apple");define("YR", 2011);
prefix.
// output: Apple 2011
echo
?>APPLE." ".YR;
Constants name are usually entirely UPPERCASED.
When should we use a variable, and when should we use a constant?
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Manipulating Variables with Operators
៚ Operators are symbols that tell the PHP processor to perform certain actions.
៚ PHP supports more than 50 such operators, ranging from operators for arithmetical operations to operators for logical comparison and bitwisecalculations.
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Performing Arithmetic Operations
៚ e.g. arithmeticOperations.php<?php
echo 3 + 2; // output: 5
echo 3 - 2; // output: 1
echo 3 * 2; // output: 6
echo 3 / 2; // output: 1.5
echo
?>3 % 2; // output: 1
Is there any limit on how large a PHP integer value can be?
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Arithmetic Operators
Operator Description
+ Add
- Subtract
* Multiply
/ Divide
% Modulus
Concatenating Strings
៚ e.g. concatenatingStrings.php
<?php$apple = "Apple";$banana = "Banana";
// use (.) to join strings into 1
$fruits = $apple." and ".$banana;
// output: I love apple and
".$fruits.".";banana..
echo
?>"I love
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Comparing Variables
៚ e.g. comparingVariables.php<?php$num = 6; $num2 = 3; $str = "6";
// output:echo ($num// output:echo ($num
0<1>
(false)
$num2); (true)$num2);
// output:echo ($num
0<
(false)$str);
// output:echo ($num// output:echo ($num?>
1 (true)== $str);0 (false)=== $str);
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Comparison Operators
Operator Description
== Equal to
!= Not equal to
> Greater than
>= Greater than or equal to
< Less than
<= Less than or equal to
=== Equal to and of the same type
Performing Logical Tests
៚ e.g. performingLogicalTests.php<?php
// output:
echo (true// output:echo (true// output:
1 (true)
&& true);0 (false)&& false);0 (false)
echo (false && false);
// output: 1 (true)
echo (false || true);
// output: 0 (false)
echo (!true);?>
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Logical Operators
Operator Description
&& AND
|| OR
! NOT
Other Useful Operators
៚ e.g. otherUsefulOperators.php
<?php$count = 7; $age = 60; $greet = "We";
Increased by 1: ++Decreased by 1: --
$count -= 2;
// output: 5 echo $count;
e.g. $count++; // $count = $count + 1;
$age /= 5;
// output: 12 echo $age;
$greet .= "lcome!";
// output: Welcome!echo $greet;?>
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Assignment Operators
Operator Description
+= Add, assign
-= Subtract, assign
*= Multiply, assign
/= Divide, assign
%= Modulus, assign
.= Concatenate, assign
Understanding Operator Precedence
៚ Operators at the same level have equal precedence:
៙ ++
៙ !
៙ *
៙ +
៙ <
៙ ==
៙ &&
៙ || ៙ =
--
/
-<=!=
%
.> >==== !==
+= -= *= /= .= %= &= |= ^=
៚ Parentheses (
៚ e.g.
៙ 3 + 2 * ៙ (3 + 2)
): force PHP to evaluate it first
5; // 3 + 10 = 13
* 5; // 5 * 5 = 25
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Handling Form Input
៚ e.g. chooseCar.html
<form name="fCar" method="POST" action="getCar.php">
<select name="selType"><option value="Porsche">Porsche</option><option value="Ford">Ford</option>
</select> Color:<input
<input</form>
type="text" name="txtColor" />type="submit" value="get Car" />
action="getCar.php"Reference a PHP script
method="POST" Submission via POST GET: method="GET"
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Handling Form Input (cont.)
៚ e.g. getCar.php
<?php// get values via $_POST | $_GET$type = $_POST["selType"];$color = $_POST["txtColor"];echo $color." ".$type;
?>
$_POST[fieldName];
$_POST: a special container variable (array) is used to get a value of a fieldof a form sent by using the POST method (or $_GET for the GET method).fieldName: the field whose value will be get/assigned to a variable.
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The End
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The End