PHP error guide

Lost connection to MySQL server during query: meaning and fix

error sqlstate Affects: PDO with MySQL/MariaDB; exact server wording varies Last verified:

Error summary

Investigate server logs, query duration, network resets, and packet limits. The connection drops while a query or result transfer is active.

What it means

Investigate server logs, query duration, network resets, and packet limits. The connection drops while a query or result transfer is active.

What the error means

This message means that the connection drops while a query or result transfer is active. The exact signature distinguishes lost connection to mysql server during query from a generic application failure.

Why PHP produces it

The engine or service reports “Lost connection to MySQL server during query” because its required precondition was not met. Investigate server logs, query duration, network resets, and packet limits.

PHP version notes

The lost connection to mysql server during query wording here is based on PDO with MySQL/MariaDB; exact server wording varies; punctuation and exception class names can differ on older branches or vendor builds.

Most common causes

  • The immediate input or configuration reaches the specific condition: the connection drops while a query or result transfer is active
  • The code path assumes the prerequisite for lost connection to mysql server during query has already been satisfied.
  • For lost connection to mysql server during query, development and production differ in version, extension, permissions, paths, or service configuration.
  • An earlier operation returned an unchecked value that is consumed by the line reporting lost connection to mysql server during query.

Minimal examples

BAD — reproduces the problem

php 
$rows = $pdo->query("SELECT * FROM huge_log")->fetchAll();

FIXED — safer pattern

php 
$stmt = $pdo->query("SELECT id FROM huge_log");
while ($id = $stmt->fetchColumn()) { processId($id); }

Step-by-step diagnosis

  1. Copy the complete “SQLSTATE[HY000]: General error: 2013 Lost connection to MySQL server during query” text and retain the first application stack frame.
  2. Reproduce lost connection to mysql server during query in the same SAPI and environment listed for this page.
  3. Before changing lost connection to mysql server during query, inspect the preceding value or directive and verify its type, path, version, and permissions.
  4. Apply the narrow correction—investigate server logs, query duration, network resets, and packet limits—then repeat the original request once.

Fixes

Correct the failing prerequisite

Investigate server logs, query duration, network resets, and packet limits

php 
$stmt = $pdo->query("SELECT id FROM huge_log");
while ($id = $stmt->fetchColumn()) { processId($id); }

Fail explicitly at the boundary

Validate the condition before the operation that emits lost connection to mysql server during query, and log a safe diagnostic without credentials or full production paths.

Common mistakes when fixing it

  • Suppressing lost connection to mysql server during query instead of correcting its upstream condition.
  • Testing lost connection to mysql server during query only with the CLI binary when the failing request runs under FPM or Apache.
  • Changing a global setting for lost connection to mysql server during query before confirming the site-specific effective configuration.

How to prevent it

  • Add a focused test that exercises the boundary responsible for lost connection to mysql server during query.
  • Keep runtime versions, extensions, configuration, and deploy artifacts affecting lost connection to mysql server during query reproducible.
  • Validate external data and service return values before they can trigger lost connection to mysql server during query.

Web server / environment notes

fpm, cli, docker, linux. The failure occurs where the connection drops while a query or result transfer is active

Tags: fpm,cli,docker,linux

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