Php Lesson 2:- Conditional Statements and Looping
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Using Conditional Statements in Php
There are 2 conditional statements in Php:
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)
switch statement - use this statement if you want to select one of many sets
of lines to execute
Using the If Statement in Php
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;
Example
The following example will output "Have a nice weekend!" if the current
day is Friday, otherwise it will output "Have a nice day!":
<html>
<body><?php
$d=date("D");
if ($d=="Fri")
echo "Have a nice weekend!";
else
echo "Have a nice day!";
?></body>
</html>
If more than one line should be executed when a condition is true, the lines
should be enclosed within curly braces:
<html>
<body><?php
$x=10;
if ($x==10)
{
echo "Hello<br />";
echo "Good morning<br />";
}
?></body>
</html>
The Switch Statement in Php
If you want to select one of many blocks of code to be executed, use the Switch
statement.
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;
}
Example
This is how it works: First we have a single expression (most often a variable),
that is evaluated once. The value of the expression is then compared with the
values for each case in the structure. If there is a match, the block of code
associated with that case is executed. Use break to prevent the code from running
into the next case automatically. The default statement is used if none of the
cases are true.
<html>
<body><?php
switch ($x)
{
case 1:
echo "Number 1";
break;
case 2:
echo "Number 2";
break;
case 3:
echo "Number 3";
break;
default:
echo "No number between 1 and 3";
}
?></body>
</html>
Using Looping in Php
In PHP you may have to use the following looping statements:
while - loops through a block of code 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
for - loops through a block of code a specified number of times
foreach - loops through a block of code for each element in
an array
The while Statement in Php
The while statement will execute a block of code if and as long a condition
is true.
Syntax
while (condition)
code to be executed;
Example
The following example demonstrates a loop that will continue to run as long
as the variable i is less than, or equal to 5. i will increase by 1 each time
the loop runs:
<html>
<body><?php
$i=1;
while($i<=5)
{
echo "The number is " . $i . "<br />";
$i++;
}
?></body>
</html>
The do...while Statement in Php
In Php 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);
Example
The following example will increment the value of i at least once, and it will
continue incrementing the variable i while it has a value of less than 5:
<html>
<body><?php
$i=0;
do
{
$i++;
echo "The number is " . $i . "<br />";
}
while ($i<5);
?></body>
</html>
The for Statement in Php
In Php the for statement is used when you know how many times you want to execute
a statement or a list of statements.
Syntax
for (initialization; condition; increment)
{
code to be executed;
}
Note: The for statement has three parameters. The first parameter is for initializing
variables, the second parameter holds the condition, and the third parameter
contains any increments required to implement the loop. If more than one variable
is included in either the initialization or the increment section, then they
should be separated by commas. The condition must evaluate to true or false.
Example
The following example prints the text "Hello World!" five times:
<html>
<body><?php
for ($i=1; $i<=5; $i++)
{
echo "Hello World!<br />";
}
?></body>
</html>
The foreach Statement in Php
In Php we can use Loops over the array given by the parameter. On each loop,
the value of the current element is assigned to $value and the array pointer
is advanced by one - so on the next loop, you'll be looking at the next element.
Syntax
foreach (array as value)
{
code to be executed;
}
Example
The following example demonstrates a loop that will print the values of of the
given array:
<html>
<body><?php
$arr=array("one", "two", "three");
foreach ($arr as $value)
{
echo "Value: " . $value . "<br />";
}
?></body>
</html>
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