The PHP PDOException is a runtime exception that occurs when something goes wrong while using the PDO (PHP Data Objects) class or its related extensions. For example, this exception can occur while handling database connections or queries.
What Causes PDOException
PHP Data Objects (PDO) are a collection of APIs that are used to access and work with databases. The PDOException is thrown anytime an issue occurs while using the PDO interface. Common situations where this exception can occur are:
- Attempting to connect to a database e.g. entering an incorrect password for the database connection.
- Issuing an SQL statement e.g. missing database table, invalid SQL statement.
PDOException Example
Here’s an example of a PHP PDOException thrown when facing issues connecting to a database using the PDO interface:
<?php
$dbh = new PDO("mysql:host=localhost;dbname=test", "user", "pass");
?>
In the above example, the PDO class is used to establish a connection to a database. Since the database connection parameters are incorrect, running the above code throws a PDOException:
PHP Fatal error: Uncaught PDOException: SQLSTATE[HY000] [2002] Connection refused in main.php:2
Stack trace:
#0 main.php(2): PDO->__construct('mysql:host=loca...', 'user', 'pass')
#1 {main}
thrown in main.php on line 2
How to Handle PDOException
The PDOException can be caught and handled using a try-catch block. The try block should contain the lines of code that can throw the exception and the catch block should catch and handle the PDOException appropriately. The message associated with the exception can be retrieved using the Exception::getMessage method on the PDOException object.
Using the above approach, the previous example can be updated to handle the error:
<?php
try {
$dbh = new PDO("mysql:host=localhost;dbname=test", "user", "pass");
} catch (PDOException $e) {
print "Error: " . $e->getMessage();
}
?>
Here, a check is performed for the PDOException using the try-catch block. When the above code is executed, the catch block catches the PDOException and handles it, producing the following output:
Error: SQLSTATE[HY000] [2002] Connection refused
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