{"id":1007,"date":"2021-04-10T09:05:03","date_gmt":"2021-04-10T09:05:03","guid":{"rendered":"https:\/\/phptutorial.net\/?page_id=1007"},"modified":"2021-05-21T13:06:45","modified_gmt":"2021-05-21T13:06:45","slug":"php-try-catch","status":"publish","type":"page","link":"https:\/\/www.phptutorial.net\/php-oop\/php-try-catch\/","title":{"rendered":"PHP try…catch"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you will learn how to use the PHP try...catch<\/code> statement to handle exceptions.<\/p>\n\n\n\n

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

In programming, unexpected errors are called exceptions. Exceptions can be attempting to read a file that doesn’t exist<\/a> or connecting to the database server<\/a> that is currently down.<\/p>\n\n\n\n

Instead of halting the script, you can handle the exceptions gracefully. This is known exception handling.<\/p>\n\n\n\n

To handle the exceptions, you use the try...catch<\/code> statement. Here’s a typical syntax of the try...catch<\/code> statement:<\/p>\n\n\n

<?php<\/span>\n\ntry<\/span> {\n\t\/\/ perform some task<\/span>\n} catch<\/span> (Exception<\/span> $ex) {\n\t\/\/ jump to this part<\/span>\n\t\/\/ if an exception occurred<\/span>\n}\n<\/span><\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
In this syntax, the try...catch<\/code> statement has two blocks: try<\/code> and catch<\/code>.<\/p>\n\n\n\n
In the try<\/code> block, you do some tasks e.g.,reading a file. If an exception occurs, the execution jumps to the catch<\/code> block.<\/p>\n\n\n\n
In the catch<\/code> block, you specify the exception name and the code to handle a specific exception.<\/p>\n\n\n\n
PHP try…catch example #<\/a><\/h2>\n\n\n\n
The following example shows how to read data from a CSV file:<\/p>\n\n\n
<?php<\/span>\n\n$data = [];\n\n$f = fopen('data.csv'<\/span>, 'r'<\/span>);\n\ndo<\/span> {\n\t$row = fgetcsv($f);\n\t$data[] = $row;\n} while<\/span> ($row);\n\nfclose($f);<\/span><\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
If the data.csv<\/code> file doesn’t exist, you’ll get many warrnings. The following shows the first warning:<\/p>\n\n\n
PHP Warning:  fopen(data.csv): failed to open stream: No such file or directory in ... on line 5<\/code><\/span>Code language:<\/span> plaintext<\/span> (<\/span>plaintext<\/span>)<\/span><\/small><\/pre>\n\n\n
\n<?php<\/span>\n\n$data = [];\n\n$f = fopen('data1.csv'<\/span>, 'r'<\/span>);\n\nif<\/span> (!$f) {\n\techo<\/span> 'The file is not accessible.'<\/span>;\n\texit<\/span>;\n}\n\ndo<\/span> {\n\t$row = fgetcsv($f);\n\tif<\/span> ($row === null<\/span>) {\n\t\techo<\/span> 'The stream is invalid.'<\/span>;\n\t\texit<\/span>;\n\t}\n\n\tif<\/span> ($row === false<\/span>) {\n\t\techo<\/span> 'Other errors occurred.'<\/span>;\n\t\texit<\/span>;\n\t}\n\n\t$data[] = $row;\n} while<\/span> ($row);\n\n\/\/ close the file<\/span>\nif<\/span> (!$f) {\n\tfclose($f);\n}\n\nprint_r($data);<\/span><\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
However, this code mixes the program logic and error handlers.<\/p>\n\n\n\n
The advantage of the try...catch<\/code> statement is to separate the program logic from the error handlers. Therefore, it makes code easier to follow.<\/p>\n\n\n\n
The following illustrates how to use the try...catch<\/code> block for reading data from a CSV file:<\/p>\n\n\n
<?php<\/span>\n\n$data = [];\n\ntry<\/span> {\n\t$f = fopen('data.csv'<\/span>, 'r'<\/span>);\n\n\tdo<\/span> {\n\t\t$row = fgetcsv($f);\n\t\t$data[] = $row;\n\t} while<\/span> ($row);\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 any error occurs in the try...block<\/code>, the execution jumps to the catch<\/code> block.<\/p>\n\n\n\n
The exception variable $ex<\/code> is an instance of the Exception<\/code> class that contains the detailed information of the error. In this example, we get the detailed error message by calling the getMessage()<\/code> method of the $ex<\/code> object.<\/p>\n\n\n\n
Multiple catch blocks #<\/a><\/h2>\n\n\n\n
A try...catch<\/code> statement can have multiple catch<\/code> blocks. Each catch<\/code> block will handle a specific exception:<\/p>\n\n\n
<?php<\/span>\n\ntry<\/span> {\n\t\/\/code...<\/span>\n} catch<\/span> (Exception1 $ex1) {\n\t\/\/ handle exception 1<\/span>\n} catch<\/span> (Exception2 $ex2) {\n\t\/\/ handle exception 2<\/span>\n} catch<\/span> (Exception1 $ex3) {\n\t\/\/ handle exception 3<\/span>\n}\n...<\/span><\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
When a try...catch<\/code> statement has multiple catch<\/code> blocks, the order of exception should be from the specific to generic. And the last catch<\/code> block should contain the code for handling the most generic exception. By doing this, the try...catch<\/code> statement can catch all the exceptions.<\/p>\n\n\n\n
If you have the same code that handles multiple types of exceptions, you can place multiple exceptions in one catch<\/code> block and separate them by the pipe (|<\/code>) character like this:<\/p>\n\n\n
<?php<\/span>\n\ntry<\/span> {\n\t\/\/code...<\/span>\n} catch<\/span> (Exception1 | Exception2 $ex12) {\n\t\/\/ handle exception 1 & 2<\/span>\n} catch<\/span> (Exception3 $ex3) {\n\t\/\/ handle exception 3<\/span>\n}<\/span><\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
By specifying multiple exceptions in the catch<\/code> block, you can avoid code duplication. This feature has been supported since PHP 7.1.0.<\/p>\n\n\n\n
Ignoring the exception variable #<\/a><\/h2>\n\n\n\n
As of PHP 8.0, the variable name for the caught exception is optional like this:<\/p>\n\n\n
<?php<\/span>\n\ntry<\/span> {\n\t\/\/code...<\/span>\n\n} catch<\/span> (Exception<\/span>) {\n\t\/\/ handle exception<\/span>\n}\n<\/span><\/code><\/span>Code language:<\/span> HTML, XML<\/span> (<\/span>xml<\/span>)<\/span><\/small><\/pre>\n\n\n
In this case, the catch<\/code> block will still execute but won’t have access the Exception<\/code> object.<\/p>\n\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
  • Use the try...catch<\/code> statement to handle exceptions. <\/li>
  • The try...catch<\/code> statement separates the program logic and exception handlers.<\/li>
  • Use multiple catch blocks to handle multiple exceptions. Place the most specific exception first and the least specific exception after.<\/li>
  • Specify a list of pipe-separated exceptions in a single catch<\/code> block if the same code can handle multiple exceptions.<\/li>
  • Ignore the exception variable when you don’t want to access the detail of the exception.<\/li><\/ul>\n
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    Did you find this tutorial useful?<\/div>\n\t\t
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To fix this, you may add an if<\/code> statement<\/a> in every step:<\/p>\n\n\n