PHP Basics

Syntax
 PHP’s

syntax derived from many languages

 More

Java-like with the latest objectoriented additions

 Designed

CPTR304: Internet Authoring

primarily as a text processor

2

PHP Tags
Standard Tags

<? php
... code
?>

Short Tags

<?
... code
?>
<?=$variable ?>

Script Tags

<script language=“php”
... code
</script>

ASP Tags

<%
... code
%>


Short tags, script tags and ASP tags are all considered deprecated.

3

Comments
// Single line comment

# Single line comment

/* Multi-line
comment
*/

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


4

Whitespaces


You can’t have any whitespaces between <? and
php



You cannot break apart keywords



You cannot break apart variable names and
function names


5

Code Block

{

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

6

Data Types
boolean

true or false

int

signed numeric integer value

float

signed floating-point value

string

collection of binary data


7

Numeric Values
Decimal

10; -11; 1452

Standard decimal notation

Octal

0666, 0100

Octal notation – identified by its
leading zero and used to mainly
express UNIX-style access
permissions

Hexadecimal

0x123; 0XFF; -0x100

Base-16 notation


8

Numeric Values, cont’d
Decimal

0.12; 1234.43; -.123

Traditional

Exponential

2E7, 1.2e2

Exponential notation – a set of
significant digits (mantissa),
followed by the case-insensitive
letter E and by an exponent.


9

Strings
 Equivalent

to text (according to many
programmers)

 Actually,

an ordered collection of binary

data


10

Booleans


Used as the basis for logical operations



Boolean conversion has special rules:
A

number converted to Boolean becomes false if the
original number is zero, and true otherwise

A

string is converted to false only if it is empty or if
it contains the single character 0

 When

converted to a number or string, a Boolean
becomes 1 if true, and 0 otherwise


11

Compound Data Types


Arrays are containers of ordered data elements;



Objects are containers of both data and code.


12

Other Data Types
 NULL

– variable has no value

– used to indicate external
resources that are not used natively by PHP

 resource


13

Type Conversion
$x = 10.88;
echo (int) $x;


14

Variables


A variable can contain any type of data



PHP is loosely typed as opposed to being strongly typed
like C, C++, and Java



Identified by a dollar sign $, followed by an identifier
name


$name = „valid‟; //valid identifier



$_name = „valid‟; //valid identifier



$1name = „invalid‟; //invalid identifier, starts
with a number


15

Variable Variables


A variable whose name is contained in another variable

$name = „foo‟;
$$name = „bar‟;

echo $foo; //Displays „bar‟


16

Variable Variables, cont’d
$name = „123‟;
/* 123 is your variable name, this would normally
be invalid. */
$$name = „456‟;
// Again, you assign a value
echo ${„123‟};
//Finally, using curly braces you can output „456‟

17

Variable Variables, cont’d
function myFunc() {
echo „myFunc!‟;

}
$f = „myFunc‟;

$f(); //will call myFunc();


18

Determining If a Variable Exists
Use the special construct isset()
echo isset ($x);


19

Referencing Variables

$a = 10;

$b = &$a;

//by reference

$b = 20;
echo $a;


//Outputs 20

20

Constants
define(„EMAIL‟, „davey.php.net‟); //Valid name
echo EMAIL;
define („USE_XML‟, true);
if(USE_XML) {

}

define („1CONSTANT‟, „some value‟); //Invalid

21

Operators


Assignment



Arithmetic



String



Comparison



Logical


22

Additional Operators
 Bitwise
 Error

– manipulating bits using Boolean math

Control – error suppression

 Execution

– executing system commands

 Incrementing/Decrementing

 Type

– identifying Objects


23

String Concatenation
$string = “foo” . “bar”;
$string2 = “baz”;
$string .= $string2;
echo $string;

24

Bitwise Operators
&

Bitwise AND

|

Bitwise OR

^

Bitwise XOR

<<

Bitwise left shift

>>

Bitwise right shift


25

$x = 1;
echo $x << 1; //Outputs 2
$x = 8;
echo $x >> 1; //Outputs 4
echo $x >> 2; //Outputs 2

26

$x = 1;

echo $x * pow(2, 32); //Outputs 4,294,967,296


27

Comparisons
==

Equivalence – evaluates to true if both operands have the
same value but not necessarily the same type.

===

Identity – evaluates to true only if the operands are of the
same type and contain the same value.

!=

Not-equivalent – evaluates to true if the operands are not
equivalent, without regards to their type.

!==

Not-identical – evaluates to true if the operands are not of
the same type or contain the same value.


28

Logical Operators
 &&

/ and
 || / or
 XOR


29

Error Suppression Operator
$x = @mysql_connect();


30

Conditional Structures


Decision-making





if-then-else

switch

Iteration


while()



do...while()



for


31

if-then-else
if (expression1) {
} elseif (expression2){

} else {
}

32

Ternary Operator
echo 10 == $x ? „Yes‟ : „No‟;

if (10
echo
} else
echo
}

== $x){
„Yes‟;
{
„No‟;
33

Switch
$a = 0;
switch ($a) {

case true:
break;
case 0:
break;
default:
break;
}

34

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

}


35

do…while()
$i = 0;
do {
echo $i . PHP_EOL;
$i++;

} while ($i < 10)


36

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


37

Errors and Error Management
Compile-time errors Detected by parser while compiling a script.
Cannot be trapped within the script itself.
Fatal errors

Halt the execution of a script. Cannot be trapped.

Recoverable errors

Represent significant failures but can be handled
in a safe way.

Warnings

Recoverable errors that indicate a run-time fault.
Does not halt execution.

Notices

Indicates that an error condition has occurred but
is not necessarily significant. Does not halt script
execution.
38


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