php basics

PHP BasicsHenry Osborne

CPTR304: Internet Authoring 2

Syntax

PHP’s syntax derived from many languages

More Java-like with the latest object-oriented additions

Designed primarily as a text processor


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.


Comments

// Single line comment # Single line comment

/* Multi-linecomment*/

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


Whitespaces

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

You cannot break apart keywords You cannot break apart variable names and

function names


Code Block

{

//Some comments

f(); // a function call

}


Data Types

boolean true or false

int signed numeric integer value

float signed floating-point value

string collection of binary data


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


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.


Strings

Equivalent to text (according to many programmers)

Actually, an ordered collection of binary data


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


Compound Data Types

Arrays are containers of ordered data elements;

Objects are containers of both data and code.


Other Data Types

NULL – variable has no value

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


Type Conversion

$x = 10.88;

echo (int) $x;


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


Variable Variables

A variable whose name is contained in another variable

$name = ‘foo’;

$$name = ‘bar’;

echo $foo; //Displays ‘bar’


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’


Variable Variables, cont’d

function myFunc() {

echo ‘myFunc!’;

}

$f = ‘myFunc’;

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


Determining If a Variable Exists

Use the special construct isset()

echo isset ($x);


Referencing Variables

$a = 10;

$b = &$a; //by reference

$b = 20;

echo $a; //Outputs 20


Constants

define(‘EMAIL’, ‘davey.php.net’); //Valid name

echo EMAIL;

define (‘USE_XML’, true);

if(USE_XML) { }

define (‘1CONSTANT’, ‘some value’); //Invalid


Operators

Assignment Arithmetic String Comparison Logical


Additional Operators

Bitwise – manipulating bits using Boolean math

Error Control – error suppressionExecution – executing system commandsIncrementing/DecrementingType – identifying Objects


String Concatenation

$string = “foo” . “bar”;

$string2 = “baz”;

$string .= $string2;

echo $string;


Bitwise Operators

& Bitwise AND

| Bitwise OR

^ Bitwise XOR

<< Bitwise left shift

>> Bitwise right shift


$x = 1;

echo $x << 1; //Outputs 2


$x = 8;

echo $x >> 1; //Outputs 4

echo $x >> 2; //Outputs 2


$x = 1;


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


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.


Logical Operators

&& / and|| / orXOR


Error Suppression Operator

$x = @mysql_connect();


Conditional Structures

Decision-making

if-then-else

switch

Iteration

while()

do...while()

for


if-then-else

if (expression1) {

} elseif (expression2){

} else {

}


Ternary Operator

echo 10 == $x ? ‘Yes’ : ‘No’;

if (10 == $x){

echo ‘Yes’;

} else {

echo ‘No’;

}


Switch

$a = 0;

switch ($a) {

case true:

break;

case 0:

break;

default:

break;

}


while()

$i = 0;

while ($i < 10) {

echo $i . PHP_EOL;

$i++;

}


do…while()

$i = 0;

do {

echo $i . PHP_EOL;

$i++;

} while ($i < 10)


for()

for ($i = 0; $i < 10; $i++) {

echo $i . PHP_EOL;

}


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.

PHP Basics

php basics

Education

php basics henry osborne

internet authoringprimarily

languages morejava

text processor2

syntax phpssyntax