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When using MySQL databases in PHP, the mysqli extension provides rich functionality to handle database operations. mysqli::get_warnings is one of the very practical functions that can help developers obtain warning information generated by the database after executing SQL statements, so as to better debug and optimize. This article will take you to quickly understand the basic usage and precautions of mysqli::get_warnings .
The mysqli::get_warnings function is used to return an object ( mysqli_warning ) containing all warning information generated by the current connection, which are usually some non-fatal hints after the MySQL execution statement. For example, when inserting data, there is a data truncation or a data type mismatch, but the SQL statement itself has no errors.
Getting these warnings helps developers spot potential problems and avoid program exceptions or data exceptions.
The following example demonstrates how to use mysqli::get_warnings to get warning information.
<?php
$mysqli = new mysqli("gitbox.net", "username", "password", "database");
if ($mysqli->connect_error) {
die("Connection failed: " . $mysqli->connect_error);
}
// Execution may generate warningsSQLStatement，For example, data types do not match
$sql = "INSERT INTO users (id, name) VALUES (1, 'Zhang San'), (2, 'Li Si'), (3, 'Wang Wu')";
if ($mysqli->query($sql) === TRUE) {
echo "Insert successfully\n";
// Get warning information
if ($warn = $mysqli->get_warnings()) {
do {
echo "Warning number: " . $warn->errno . "\n";
echo "Warning message: " . $warn->message . "\n";
} while ($warn->next());
} else {
echo "No warning\n";
}
} else {
echo "mistake: " . $mysqli->error;
}
$mysqli->close();
?>
mysqli::get_warnings returns a mysqli_warning object, and null if there is no warning.
Get the warning code via $warn->errno .
Get the warning description via $warn->message .
Iterate through all warnings via the $warn->next() method.
Capture warnings when data is inserted or updated <br> When inserting data, if the field type does not match or the data is truncated, the SQL statement may be executed successfully but generates a warning. At this time, use get_warnings to capture this information.
Debugging complex SQL statements <br> Some complex queries or updates may cause warnings, such as foreign key constraints not met or character encoding issues. Using this function can help locate the problem.
mysqli::get_warnings is a very useful debugging tool that helps developers capture MySQL warning messages. It is very critical to troubleshooting potential database problems and ensuring program stability. I hope that through the introduction of this article, you can quickly master the usage skills of mysqli::get_warnings and improve the quality of PHP database programming.
