DAY - 6
Flow control and Loops
PHP supports following three decision making (Flow control ) statements –
·
if...else
statement − use this statement if you want to
execute a set of code when a condition is true and another if the condition is
not true
·
elseif
statement − is used with the if...else statement
to execute a set of code if one of the several condition is
true
·
switch
statement − is used if you want to select one of
many blocks of code to be executed, use the Switch statement. The switch
statement is used to avoid long blocks of if..elseif..else code.
The If...Else Statement
If you want to execute some code if a
condition is true and another code if a condition is false, use the if....else
statement.
Syntax
if (condition)
code to be executed if condition is true;
else
code to be executed if condition is false;
The ElseIf Statement
If you want to execute some code if
one of the several conditions are true use the elseif statement
Syntax
if (condition)
code to be executed if condition is true;
elseif (condition)
code to be executed if condition is true;
else
code to be executed if condition is false;
The Switch Statement
If you want to select one of many
blocks of code to be executed, use the Switch statement.
The switch statement is used to avoid
long blocks of if..elseif..else code.
Syntax
switch (expression){
case label1:
code to be executed if expression = label1;
break;
case label2:
code to be executed if expression = label2;
break;
default:
code to be executed
if expression is different
from both label1 and label2;
}
Loops in PHP are used to execute the
same block of code a specified number of times. PHP supports following four
loop types.
·
for − loops
through a block of code a specified number of times.
·
while − loops through a block of code if and as long as a
specified condition is true.
·
do...while − loops through a block of code once, and then repeats the
loop as long as a special condition is true.
·
foreach − loops through a block of code for each element in an
array.
The for loop statement
The for statement is used when you
know how many times you want to execute a statement or a block of statements.
Syntax
for (initialization; condition; increment){
code to be executed;
}
The initializer is used to set the
start value for the counter of the number of loop iterations. A variable may be
declared here for this purpose and it is traditional to name it $i.
The while loop statement
The while statement will execute a
block of code if and as long as a test expression is true.
If the test expression is true then
the code block will be executed. After the code has executed the test
expression will again be evaluated and the loop will continue until the test
expression is found to be false.
Syntax
while (condition) {
code to be executed;
}
The do...while loop statement
The do...while statement will execute
a block of code at least once - it then will repeat the loop as long as a
condition is true.
Syntax
do {
code to be executed;
}
while (condition);
The foreach loop statement
The foreach statement is used to loop
through arrays. For each pass the value of the current array element is
assigned to $value and the array pointer is moved by one and in the next pass
next element will be processed.
Syntax
foreach (array as value) {
code to be executed;
}
The break statement
The PHP break keyword
is used to terminate the execution of a loop prematurely.
The break statement
is situated inside the statement block. It gives you full control and whenever
you want to exit from the loop you can come out. After coming out of a loop
immediate statement to the loop will be executed.
The continue statement
The PHP continue keyword
is used to halt the current iteration of a loop but it does not terminate the
loop.
Just like the break statement
the continue statement is situated inside the statement block
containing the code that the loop executes, preceded by a conditional test. For
the pass encountering continue statement, rest of the loop
code is skipped and next pass starts.
