PHP mysqli_error() Function: Usage and Examples

Returns the most recent error message reported for the connection.

The examples focus on the operation itself, including the important distinction: mysqli_report configures how MySQLi reports failures.

What It Does

Use the examples below to observe the behavior on a small dataset before extending it to application code.

Syntax and Return Value

mysqli_error(...) — requires the corresponding optional extension

The displayed signature describes the API or identifies any correction or optional dependency. When a parameter is optional, supply it only when the task requires it.

Example 1: Basic Use

This legacy error retrieval can be empty under exception-driven code. Prefer catching mysqli_sql_exception.

<?php
$link = mysqli_connect(getenv('DB_HOST') ?: '127.0.0.1', getenv('DB_USER') ?: 'app', getenv('DB_PASSWORD') ?: '', getenv('DB_NAME') ?: 'demo');
mysqli_set_charset($link, 'utf8mb4');
try { mysqli_query($link, "SELECT missing_column FROM users"); } catch (mysqli_sql_exception $e) {
    error_log("Database query failed: " . $e->getCode());
}
echo mysqli_error($link);

This example is meant for a configured application environment; output depends on the installed extension, external service, or database contents.

Example 2: Checking Behavior

This legacy error retrieval can be empty under exception-driven code. Prefer catching mysqli_sql_exception. Error number, text and strict exception mode describe different aspects of a failed operation.

<?php
$link = mysqli_connect(getenv('DB_HOST') ?: '127.0.0.1', getenv('DB_USER') ?: 'app', getenv('DB_PASSWORD') ?: '', getenv('DB_NAME') ?: 'demo');
mysqli_set_charset($link, 'utf8mb4');
try { mysqli_query($link, "SELECT missing_column FROM users"); } catch (mysqli_sql_exception $e) {
    error_log("Database query failed: " . $e->getCode());
}
echo mysqli_errno($link);

This example is meant for a configured application environment; output depends on the installed extension, external service, or database contents.

Example 3: Practical Example

This legacy error retrieval can be empty under exception-driven code. Prefer catching mysqli_sql_exception. Error number, text and strict exception mode describe different aspects of a failed operation.

<?php
$link = mysqli_connect(getenv('DB_HOST') ?: '127.0.0.1', getenv('DB_USER') ?: 'app', getenv('DB_PASSWORD') ?: '', getenv('DB_NAME') ?: 'demo');
mysqli_set_charset($link, 'utf8mb4');
try { mysqli_query($link, "SELECT missing_column FROM users"); } catch (mysqli_sql_exception $e) {
    error_log("Database query failed: " . $e->getCode());
}
echo "Use exception handling for SQL errors";

This example is meant for a configured application environment; output depends on the installed extension, external service, or database contents.

Important Behavior and Edge Cases

With MYSQLI_REPORT_STRICT, many operations throw mysqli_sql_exception instead of requiring error checks.

This API is supplied by an optional extension that is not installed in the local test runtime, or requires a different PHP version. The example must be verified in a matching environment.

Comparison with Related Approaches

Common Beginner Mistakes

Key Takeaways

• Returns the most recent error message reported for the connection.
• With MYSQLI_REPORT_STRICT, many operations throw mysqli_sql_exception instead of requiring error checks.
• mysqli_report configures how MySQLi reports failures.

Use mysqli_error when its documented behavior matches the problem. Test the relevant edge cases in your own runtime before deploying it.