{"id":194,"date":"2018-07-12T12:16:02","date_gmt":"2018-07-12T12:16:02","guid":{"rendered":"http:\/\/itp9.epgpbooks.inflibnet.ac.in\/?post_type=chapter&p=194"},"modified":"2018-12-07T11:08:46","modified_gmt":"2018-12-07T11:08:46","slug":"exception-handling","status":"publish","type":"chapter","link":"https:\/\/ebooks.inflibnet.ac.in\/itp9\/chapter\/exception-handling\/","title":{"rendered":"Exception Handling"},"content":{"raw":"
\"epgp<\/a>\r\n<\/span><\/div>\r\n
\r\n\r\n \r\n\r\n \r\n\r\n \r\n

Generally you believe that the program written by you is error free and will execute successfully. However, in few cases the program can terminate while it is executing. For example, if we have written a program which connects to a particular website and download the web pages. In normal condition, the program will execute as we expected but suppose the program runs on a computer which has not internet connection then the program will produce unexpected output. There can be similar situation, where the program open a file to read it, but the file is not exists. Such cases are known as exception. Exception result in abnormal execution and it may lead to abnormally terminate the program.<\/p>\r\n \r\n

Exceptions are runtime errors. When writing the code, you should consider any unexpected runtime error. Exception handling allows the program to execute as there is no error in the code or it can terminate the program gracefully.<\/p>\r\n \r\n\r\nTypes of error<\/strong>\r\n\r\n \r\n\r\nThere are 2 types of error.\r\n\r\n \r\n\r\n1. Syntax error\r\n\r\n2. Runtime error\r\n\r\n \r\n

Syntax errors occur when there is the syntax is not correct in the code. For exmplae, instead of echo statement, it is written as ehco.<\/p>\r\n \r\n\r\n<?php\r\n\r\n$p = 1000;\r\n\r\n$rate = 10;\r\n\r\n$n = 2;\r\n\r\n$si = ($p*$r*$n)\/100;\r\n\r\nehco \"Simple Interest for Principal $p, rate $rate for duration $n is : $si\";\r\n\r\n?>\r\n\r\n \r\n\r\nThe output is:\r\n\r\n \r\n

( ! )<\/span> Parse error: syntax error, unexpected '\"' in H:\\wamp\\www\\PathshalaWAD\\Exception Handling\\1. types of error.php on line 6<\/em><\/p>\r\n \r\n

Runtime errors are errors which occur during the execution of program. For example, in the program you want to display the value of array element which does not exists.<\/p>\r\n \r\n\r\n<\/div>\r\n

\r\n

\u00a0 \u00a0 <?php<\/p>\r\n

$cities = array('Ahmedabad','Rajkot','Surat','Vadodara');<\/p>\r\n

$count = count($cities);<\/p>\r\n

for($i=0;$i<=$count;$i++)<\/p>\r\n

{<\/p>\r\n

echo $cities[$i].\"<br>\";<\/p>\r\n

}<\/p>\r\n

?><\/p>\r\n

The output is:<\/p>\r\n

Ahmedabad<\/p>\r\n

Rajkot<\/p>\r\n

Surat<\/p>\r\n

Vadodara<\/p>\r\n\"\"\r\n\r\n \r\n

A program may have logical errors. Logical error is a error in which program execute without any error but the output is not as per expectation. For example, in following program as per simple interest formula<\/p>\r\n \r\n

$si = ($p*$r*$n)\/100 it is divided by 10. Hence though the program execute without any error but instead of correct simple interest 200 it displays 2000.<\/p>\r\n \r\n\r\n<?php\r\n\r\n$p = 1000;\r\n\r\n$r = 10;\r\n\r\n$n = 2;\r\n\r\n$si = ($p*$r*$n)\/10;<\/span>\r\n\r\necho \"Simple Interest for Principal $p, interets rate $r for duration $n is : $si\";<\/span>\r\n\r\n?><\/span>\r\n\r\n<\/div>\r\n

\r\n\r\n \r\n\r\nThe output is:\r\n\r\n \r\n\r\nSimple Interest for Principal 1000, interets rate 10 for duration 2 is : 2000\r\n\r\n \r\n\r\nException Handling<\/strong>\r\n\r\n \r\n

Exception handling is used to handle unexpected error conditions. Exception handling is changed the normal flow of the code execution if a specified error (exceptional) occurs.<\/p>\r\n \r\n\r\nException can be thrown from your own exception and then write codes to handle it.\r\n\r\n \r\n\r\nThe syntax for creating a new exception is:\r\n\r\n \r\n\r\nnew Exception ($message [, $code] )\r\n\r\n \r\n\r\n$message is a string. If $message is not string, it is converted to string.\r\n\r\n \r\n\r\n$code is optional. In case $code is not supplied, it is taken as 0(Zero).\r\n\r\n \r\n\r\nThe syntax to throw statement is:\r\n\r\n \r\n\r\nthrow $exception\r\n\r\n \r\n\r\nthrow statement is used to throw an exception object. The throw statement can throw new or existing exception.\r\n\r\n \r\n\r\nWhen an exception is occurred, then\r\n