PHP Developer''''s Dictionary- P20 pptx

Truth Table for the and Operator or Syntax variable1 or variable2 Description The or operator evaluates whether either variable1 or variable2 is true.. In understanding the truth tab

Table 4.5 Truth Table for the and Operator

or

Syntax

variable1 or variable2

Description

The or operator evaluates whether either variable1 or variable2 is true Table 4.6

contains the truth table for the possible values In understanding the truth table, you can see the only time the equation returns false is when both variable1 and

variable2 are false

Note

The only difference between this operator and the || operator is order precedence

Table 4.6 Truth Table for the or Operator

xor

Syntax

variable1 xor variable2

Description

The xor, or exclusive or operator, evaluates whether either variable1 and

variable2 , but not both, is true Table 4.7 contains the truth table for the possible values In understanding the truth table, you can see when variable1 and

variable2 are the same, false is returned

Table 4.7 Truth Table for the xor Operator

! (not)

Syntax

!variable

Description

The !, or not operator, returns the opposite of variable For instance, if variable

is true, applying the ! operator will return false

&& (and)

Syntax

variable1 && variable2

Description

The && operator evaluates whether variable1 and variable2 are true, or equal

Table 4.8 contains the truth table for the possible values In understanding the truth table, you can see the only time the equation returns true is when both variable1 and variable2 are true

Note

The only difference between this operator and the and operator is order precedence

Table 4.8 Truth Table for && Operator

|| (or)

Syntax

variable1 || variable2

Description

The || operator evaluates whether either variable1 or variable2 is true Table 4.9

contains the truth table for the possible values In understanding the truth table, you can see the only time the equation returns false is when both variable1 and

variable2 are false

Note

The only difference between this operator and the or operator is order precedence

Table 4.9 Truth Table for the || Operator

String

The string operators are used to perform manipulation on the string data types Although some of the previous operators discussed in this section can be performed

on strings as well, these are limited to strings only

Syntax

string1 string2

Description

The ., or concatenation operator, will "add" string2 to string1 when applied For

instance, if string1 ="P" and string2 ="HP", string1 string2 would equal

"PHP"

$string1 = "hel";

$string2 = "p";

$string3 = "lo";

$result1 = $sting1 $string2; // $result1 has "help"

$result2 = $sting1 $string3; // $result2 has "hello"

.= (Concatenating Assignment)

Syntax

string1 = string2

Description

The , or concatenating assignment operator, will "add" string2 to string1 when

applied and then store the new string in string1 For instance, if string1 ="P" and

string2 ="HP", then string1 = string2 would equal "PHP" and that would be the new value of string1

Predefined Variables

Predefined variables in PHP refer to language elements that are consistent across all applications run in that environment This is very much like the environment variables you see within the UNIX and Windows operating systems (Type env at a command line to see a list of your operating system variables.)

Apache

The Apache predefined variables reflect the environment settings of your Apache Web server when running PHP There are also variables that reflect information about a request of a given user-agent, or browser This enables you to grab the requested URL, query string, or another element of the HTTP request

DOCUMENT_ROOT

Syntax

string DOCUMENT_ROOT

Description

The DOCUMENT_ROOT variable contains the document root, as defined in the PHP configuration file, under which the current script is being parsed

GATEWAY_INTERFACE

Syntax

string GATEWAY_INTERFACE

Description

The GATEWAY_INTERFACE variable contains the version of the Common Gateway Interface (CGI) specification that the server is using For instance, CGI/1.1 is a valid GATEWAY_INTERFACE

HTTP_ACCEPT

Syntax

string HTTP_ACCEPT

Description

The HTTP_ACCEPT variable contains the contents of the HTTP Accept: header if the user-agent sent it to the server

HTTP_ACCEPT_CHARSET

Syntax

string HTTP_ACCEPT_CHARSET