PHP Developer''''s Dictionary- P4 docx

The continue statement enables you to stop the execution of the current control iteration and break out to the beginning for the next iteration.. For instance, if you used a continue sta

The continue statement enables you to stop the execution of the current control iteration and break out to the beginning for the next iteration The optional num value

can be used to tell the parser how many control structures to continue out of For instance, if you used a continue statement inside a while statement that was inside

a second while statement itself, you could use continue 2 to break out of both statements Using continue 1, which is the default implied value when not passed, would simply cause you to continue out of the second, or nested, while statement if($num == 5){ // continue statement will come back here if executed // do something here

if($string == "go"){

// do more here

$string = "stop";

continue 2; // breaks outside of both if statements back to first

if

}

$num++;

}

do while

Syntax

do{

code

}while(condition)

Description

The do while loop is just like the while loop except that it evaluates the

condition after the execution of the loop rather than before The effect of this is

that you are guaranteed that the loop will execute at least once, whereas the while loop does not allow for this

else

Syntax

if(condition){

code

[

}elseif(condition){

code

]

}else{

code

}

Description

The else statement, which extends the if or elseif statements, provides a default set of code to be executed if previous if or elseif statements fail condition The brackets around the elseif portion of the syntax example show that this is an optional part of a statement, whereas the if portion is required for the else statement

elseif

Syntax

if(condition){

code

}elseif(condition){

code

[

}else{

code

]

}

Description

The elseif statement, which extends the if statement, provides a second evaluation on a second condition before a set of code is to be executed This

assumes that previous if or other elseif statements fail their respective condition The brackets around the else portion of the syntax example show that this is an optional part of a statement, whereas the if portion is required for the elseif statement

for

Syntax

for([assignment];[condition];[change_assignment]{

code

}

Description

The for loop has been labeled as the most complex looping structure not only in PHP, but in other programming languages as well This loop takes an initial

assignment where a variable is assigned a value The second parameter specifies a condition that is evaluated before each iteration of the loop If the condition

evaluates to true, the code is executed and the change_assignment , such as

increasing or decreasing the assignment by 1, is performed At that time, the condition is reevaluated with the new value of the assignment and the process

repeats itself This continues until condition is false

These parameters are all optional, which might come as a surprise Leaving them, or even just condition , blank will cause the for to loop indefinitely, but does allow you to use an internal break statement to end the loop You can also see the for : endfor entry for a different syntactical way to use the for loop

Note

If you want to get extra tricky with the for loop, you can also include comma-separated code to be executed in the change_assignement For

instance, you could use print $counter, $counter++ to print the

$counter value on each iteration through the loop For more information about what the ++ means in this example, see the "Incrementing and Decrementing" section later in this chapter

for : endfor

Syntax

for([assignment];[condition];[change_assignment]):

code

endfor

Description

The for : endfor loop is an alternative syntax for the for loop Using this method, the opening and closing braces are replaced with : and endfor, respectively See the for entry for more information on condition and code

foreach

Syntax

foreach(array as current_value){

code

}

foreach(array as current_key => current_value){

code

}

Description

The foreach loop, which was added in PHP4, has two syntactical definitions In both definitions the loop takes an array and iterates through it In doing so, it stores the current_value so that it can be referenced and processed in code For associative

arrays, you can use the second syntactical definition to also store the corresponding

current_key for processing in code The following example should help clarify: // create an array

$weekdays = array (

"Sunday" => 0,

"Monday" => 1,

"Tuesday" => 2,

"Wednesday" => 3,

"Thursday" => 4,

"Friday" => 5,

"Saturday" => 6

);

// print out each day with the number it is associated with

foreach($weekday as $day => $number) {

print "\ $weekday = $day.\ n";

}

if

Syntax

if(condition){

code

}

[

elseif(condition){

code

}else{

code

}

]

Description

The if statement enables you to execute code based on successful validation of condition This statement is one of the most widely used statements in any

programming language, and PHP is no different Optionally, as the syntax description

shows, it is often used in conjunction with elseif and/or else statements to provide addition levels of control over code execution

if : endif

Syntax

if(condition):

code

endif;

Description

The if : endif statement is an alternative syntax for the if statement Using this method, the opening and closing braces are replaced with : and endif, respectively See the entry for if for more information on condition and code

include()

Syntax

include(string filename)

Description

The include() function enables you to include other files specified by filename

These secondary files can be valid PHP code or any text, such as HTML If you do have additional PHP code that needs to be executed, be sure that you use the proper beginning and ending PHP tags or the parser will not execute the code

The require() language construct has similar capabilities The major difference is that include() is executed each time it is encountered, whereas require() pulls in the contents of the included file once You can see the difference if you place these functions in the body of a loop statement

Tip

You can place a return statement in the included file to terminate the parsing of the file and return to the file that performed the inclusion

require()

Syntax