PHP uses pdo to obtain insert id. This method may have concurrency issues.

//Call the prepare method to prepare the query
$stmt = $pdo->prepare($sql);

//Pass an array to bind values ​​to the named parameters in the preprocessing query and execute SQL
$stmt->execute(array(':name' => '王五'));

//Get the ID value of the last inserted data
echo $pdo->lastInsertId() . '
';

This method may have concurrency issues

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//Call the prepare method to prepare the query
$stmt = $pdo->prepare($sql);

//Pass an array to bind values ​​to the named parameters in the preprocessing query and execute SQL
$stmt->execute(array(':name' => '王五'));

//Get the ID value of the last inserted data
echo $pdo->lastInsertId() . '
';

This method may have concurrency issues

Every link in mysql is a session
and $pdo->lastInsertId() is to get the last insert id of the current session

This $pdo is private to you and will not access data inserted by others.
The code is executed line by line from top to bottom, even if you write a loop, there will be nothing wrong.