Common PHP PDO errors and solutions: avoid pitfalls in development

php editor Xiaoxin will introduce you to common PHP PDO errors and solutions in detail to help developers avoid common traps during project development. By learning and mastering the correct use of PDO in PHP development, the stability and efficiency of the project can be improved, and code quality and security can be ensured. Avoiding common mistakes during the development process will help improve developers' technical skills and better cope with various challenges and problems.

However, you may also encounter some errors when using PDO. These errors can be due to a variety of factors, including coding errors, database configuration errors, and even hardware failures.

Here are some common PDO errors and their solutions:

1. PDOException: This is one of the most common errors in PDO. It is usually caused by coding errors or database configuration errors. To resolve this error, you need to check your code for errors and make sure the database is configured correctly.

Demo code:

try {
$dbh = new PDO("Mysql:host=localhost;dbname=my_database", "username", "passWord");
} catch (PDOException $e) {
echo $e->getMessage();
}

2. SQLSTATE[HY000] [2002] Connection refused: This error is usually caused by an inability to connect to the database. To resolve this error, you need to ensure that the database is running and that you have the correct connection information.

Demo code:

try {
$dbh = new PDO("mysql:host=localhost;dbname=my_database", "username", "password");
} catch (PDOException $e) {
echo $e->getMessage();
}

3. SQLSTATE[42S02] [1054] Unknown column "column_name" in "field list": This error is usually caused by using a non-existent column name in the query. To resolve this error, you need to check that the column names in the query are correct.

Demo code:

$query = "SELECT * FROM table_name WHERE column_name = "value"";
$stmt = $dbh->prepare($query);
$stmt->execute();

4. SQLSTATE[23000] [1062] Duplicate entry "value" for key "column_name": This error is usually caused by a unique constraint violation when inserting or updating data. To resolve this error, you need to ensure that the data does not violate any unique constraints.

Demo code:

$query = "INSERT INTO table_name (column_name) VALUES ("value")";
$stmt = $dbh->prepare($query);
$stmt->execute();

5. SQLSTATE[22003] [1216] Cannot add or update a child row: This error is usually caused by foreign key constraints. To resolve this error, you need to ensure that the data in the child table is consistent with the data in the parent table.

Demo code:

$query = "INSERT INTO child_table (column_name) VALUES ("value")";
$stmt = $dbh->prepare($query);
$stmt->execute();

The above is the detailed content of Common PHP PDO errors and solutions: avoid pitfalls in development. For more information, please follow other related articles on the PHP Chinese website!