Concept of Exception
Exception handling is used to change the normal flow of the code
execution if a specified error (exceptional) condition occurs.
Different error handling methods
- Basic use of exceptions
- Creating a custom exception handler
- Multiple exceptions
- Re-throwing an exception
- Setting a top level exception handler
Basic use of Exceptions
When an exception is thrown, the code
following it will not be executed, and PHP will try to find the matching "catch"
block.
Lets us see the concept with the example:
<html>
<body
bgcolor="pink">
<center>
<h3>
Basic use of Exceptions
<h3>
<hr>
<?php
//create function with an exception
function
checkNum($number)
{
if($number>1)
{
throw new
Except
ion("Value
must be 1 or below");
}
return
true;
}
//trigger exception
checkNum(2);
?>
</center>
</body>
</html>
Save it as basic.php
Output of above
To run the code, Open the XAMPP server and start the services like Apache and
MySQL. Open the browser type: http://localhost/yourfoldername/basic.php
![basic exception.gif]()
The above output shows, the
code get an exception which is uncaught exception.
Try, throw and catch in PHP
Here in this section we will understand the
concept to avoid the error from the above scripting , we need to create the
proper code to handle an exception.
- Try - A function using an exception should
be in a "try" block.
- Throw - This is how you trigger an
exception. Each "throw" must have at least one "catch".
- Catch - A "catch" block retrieves an
exception and creates an object containing the exception information.
Let us see the above concept with the try,
throw and catch :
<html>
<body
bgcolor="pink">
<center>
<h3>
Basic use of Exceptions with Try, Throw and catch
<h3>
<hr>
<?php
//create function with an exception
function
checkNum($number)
{
if($number>1)
{
throw new
Exception("Value
must be 1 or below");
}
return
true;
}
//trigger exception in a "try" block
try
{
checkNum(2);
//If the exception is thrown, this text will not be shown
echo
'If you
see this, the number is 1 or below';
}
//catch exception
catch(Exception
$e)
{
echo
'Message:
'
.$e->getMessage();
}
?>
</center>
</body>
</html>
Save it as basic.php
Output of above scripting
To run the code, Open the XAMPP server and start the services like Apache and
MySQL. Open the browser type: http://localhost/yourfoldername/basic.php
![basic exception1.gif]()
Further Error handling methods you will learn in my coming articles.
Thanks !!