Friday 15 March 2013

PHP Functions and Statment

The strpos() function


The strpos() function is used to search for a character/text within a string.
If a match is found, this function will return the character position of the
first match. If no match is found, it will return FALSE.

Let's see if we can find the string "world" in our string:

<?php
echo strpos("Hello world!","world");
?>

The output of the code above will be:
6

The position of the string "world" in the example above is 6. The reason
that it is 6 (and not 7), is that the first character position in the string is
0, and not 1.

Conditional Statements


Very often when you write code, you want to perform different actions for
different decisions.
You can use conditional statements in your code to do this.
In PHP we have the following conditional statements:

if statement - use this statement to execute some code only if a
specified condition is true

•if...else statement - use this statement to execute some code if a
condition is true and another code if the condition is false

•if...elseif....else statement - use this statement to select one of
several blocks of code to be executed

•switch statement - use this statement to select one of many
blocks of code to be executed

The if Statement


Use the if statement to execute some code only if a specified condition is
true.
Syntax
if (condition) code to be executed if condition is true;
The following example will output "Have a nice weekend!" if the current
day is Friday:

<html>
<body>

<?php
$d=date("D");
if ($d=="Fri") echo "Have a nice weekend!";
?>

</body>
</html>

Notice that there is no ..else.. in this syntax. The code is executed only if
the specified condition is true.

The if...else Statement


Use the if....else statement to execute some code if a condition is true
and another code if a condition is false.
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 if a condition is true/false, the
lines should be enclosed within curly braces:

<html>
<body>
<?php
$d=date("D");
if ($d=="Fri")
{
echo "Hello!<br />";
echo "Have a nice weekend!";
echo "See you on Monday!";
}

?>
</body>
</html>

The if...elseif....else Statement


Use the if....elseif...else statement to select one of several blocks of code
to be executed.
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;

Example:
The following example will output "Have a nice weekend!" if the current
day is Friday, and "Have a nice Sunday!" if the current day is Sunday.
Otherwise it will output "Have a nice day!":

<html>
<body>
<?php
$d=date("D");
if ($d=="Fri")
echo "Have a nice weekend!";
elseif ($d=="Sun")
echo "Have a nice Sunday!";
else
echo "Have a nice day!";
?>
</body>
</html>

The PHP Switch Statement


Use the switch statement to select one of many blocks of code to be
executed.
Syntax

switch (n)
{
case label1:
code to be executed if n=label1;
break;
case label2:
code to be executed if n=label2;
break;
default:
code to be executed if n is different from both label1 and
label2;
}

This is how it works: First we have a single expression n (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 no match is found.

Example
<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>

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