{"id":1011,"date":"2021-04-10T10:05:16","date_gmt":"2021-04-10T10:05:16","guid":{"rendered":"https:\/\/phptutorial.net\/?page_id=1011"},"modified":"2021-05-21T13:07:24","modified_gmt":"2021-05-21T13:07:24","slug":"php-try-catch-finally","status":"publish","type":"page","link":"https:\/\/www.phptutorial.net\/php-oop\/php-try-catch-finally\/","title":{"rendered":"PHP try…catch…finally"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use the PHP try...catch...finally<\/code> statement to handle exceptions and clean up the resources.<\/p>\n\n\n\n

Introduction to the PHP try…catch…finally statement #<\/a><\/h2>\n\n\n\n

The try…catch<\/a> statement allows you to handle exceptions. When an exception occurs in the try<\/code> block, the execution jumps to the catch<\/code> block. In the catch<\/code> block, you can place the code that handles the exception. <\/p>\n\n\n\n

The following example uses the try…catch block to read a CSV file<\/a> into an array<\/a>:<\/p>\n\n\n

<?php<\/span>\n\n$data = [];\n\ntry<\/span> {\n\t$f = fopen('data.csv'<\/span>, 'r'<\/span>);\n\n\twhile<\/span> ($row = $fgetcsv($f)) {\n\t\t$data[] = $row;\n\t}\n\n\tfclose($f);\n} catch<\/span> (Exception<\/span> $ex) {\n\techo<\/span> $ex->getMessage();\n}\n<\/span><\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
In this example, if an error occurs while reading the file, the execution jumps to the catch<\/code> block. Therefore, the following statement will never run:<\/p>\n\n\n
fclose($f);<\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
When the file is not closed properply, it may be inaccessible later.<\/p>\n\n\n\n
To ensure that the file will be closed properly regardless of whatever exception occurs or not, you can close the file in the finally<\/code> block like this:<\/p>\n\n\n
<?php<\/span>\n\n$data = [];\n\ntry<\/span> {\n\t$f = fopen('data.csv'<\/span>, 'r'<\/span>);\n\n\twhile<\/span> ($row = $fgetcsv($f)) {\n\t\t$data[] = $row;\n\t}\n} catch<\/span> (Exception<\/span> $ex) {\n\techo<\/span> $ex->getMessage();\n} finally<\/span> {\n\tif<\/span> ($f) {\n\t\tfclose($f);\n\t}\n}\n<\/span><\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
The finally<\/code> is an optional block of the try…catch statement. The finally<\/code> block always executes after the try<\/code> or catch<\/code> block.<\/p>\n\n\n\n
In this case, if an exception occurs while reading the file, the execution jumps to the catch<\/code> block to handle it and then the finally<\/code> block executes to close the file.<\/p>\n\n\n\n
The syntax of the try...catch...finally<\/code> block is as follows:<\/p>\n\n\n
<?php<\/span>\n\ntry<\/span> {\n\t\/\/ do something<\/span>\n} catch<\/span> (Exception<\/span> $e) {\n\t\/\/ code to handle exception<\/span>\n} finally<\/span> {\n\t\/\/ code to clean up the resource<\/span>\n}<\/span><\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
PHP finally & return #<\/a><\/h2>\n\n\n\n
The following defines the divide()<\/code> function that returns the division of two numbers. If an error occurs, it returns null<\/code>.<\/p>\n\n\n
<?php<\/span>\n\nfunction<\/span> divide<\/span>($x, $y)<\/span>\n<\/span>{\n\ttry<\/span> {\n\t\t$result = $x \/ $y;\n\n\t\treturn<\/span> $result;\n\t} catch<\/span> (Exception<\/span> $e) {\n\t\treturn<\/span> null<\/span>;\n\t} finally<\/span> {\n\t\treturn<\/span> null<\/span>;\n\t}\n}<\/span><\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
However, the following displays NULL instead of 5:<\/p>\n\n\n
<?php<\/span>\n\/\/ ...<\/span>\n$result = divide(10<\/span>, 2<\/span>);\nvar_dump($result); \/\/ NULL<\/span><\/span><\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
Typically, the return<\/code> statement immediately stops the execution and returns a value. However, it doesn’t work that way when it is used with the try...catch...finally<\/code> statement.<\/p>\n\n\n\n
When you use the return<\/code> statement with the try...catch...finally<\/code> statement, the finally block still executes<\/strong> after the return<\/code> statement.<\/p>\n\n\n\n
The result will be returned after the finally<\/code> block is executed. Also, if the finally<\/code> block has a return<\/code> statement, the value from the finally<\/code> block will be returned.<\/p>\n\n\n\n
The try…finally statement #<\/a><\/h2>\n\n\n\n
In the try...catch..finally<\/code> statement, either the catch<\/code> or finally<\/code> block is optional. Therefore, you can have the try...finally<\/code> statement like this:<\/p>\n\n\n
<?php<\/span> \ntry<\/span> {\n\t\/\/ do something<\/span>\n} finally<\/span> {\n\t\/\/ clean up<\/span>\n}<\/span><\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
The try...finally<\/code> statement allows you to throw an exception while cleaning up the resource appropriately.<\/p>\n\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
  • Use the try...catch...finally<\/code> statement to handle exceptions and clean up the resources.<\/li>
  • The finally<\/code> block always executes after the try or catch block.<\/li>
  • If the try<\/code> or catch<\/code> has the return<\/code> statement, the value will be returned only after the finally<\/code> block executes.<\/li><\/ul>\n
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