<?php
/* Creating Custom Exception Class */
class customException extends Exception {
    public function errorMessage() {
        //error message
        $errorMsg = 'Error on line '.$this->getLine().' in '.$this->getFile()
        .': <b>'.$this->getMessage().'</b> is not a valid E-Mail address';
        return $errorMsg;
    }
}
/* Creating Custom Exception Class */


$email = "[email protected]";
try {
    //check if
    if(!eregi("^[_a-z0-9-]+(\.[_a-z0-9-]+)*@[a-z0-9-]+(\.[a-z0-9-]+)*(\.[a-z]{2,3})$", $email)) {
        //throw exception if email is not valid
        throw new customException($email);
    }
    echo "Email Id is Valid";
} catch (customException $e) {
  //display custom message
  echo $e->errorMessage();
}
?>

Exception handling is used to change the normal flow of the code execution if a specified error (exceptional) condition occurs. This condition is called an exception.

This is what normally happens when an exception is triggered:

• The current code state is saved
• The code execution will switch to a predefined (custom) exception handler function
• Depending on the situation, the handler may then resume the execution from the saved code state, terminate the script execution or continue the script from a different location in the code

We will show 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

Note: Exceptions should only be used with error conditions, and should not be used to jump to another place in the code at a specified point.

<?php
/* Function to Throw an Exception */
function checkNum($number) {
    if($number>1) {
        throw new Exception("Value must be 1 or below");
    }
    return true;
}
/* Function to Throw an Exception */

//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 $e) {
    echo 'Message: ' .$e->getMessage();
}
?>