How to Resolve the 'Commands out of Sync' Error in MySQLi When Using Nested Queries?

Error: "Commands out of Sync" while Using MySQLi

Problem:

An attempt to execute multiple MySQLi queries simultaneously triggers the "Commands out of sync" error. The nested queries retrieve hierarchical data.

Cause:

MySQL does not allow executing new queries while rows from an in-progress query remain unfetched.

Solution:

Option 1: Use mysqli_store_result()

$result = mysqli_store_result($db);
// Execute subsequent queries

This buffers the rows in the MySQL client, allowing multiple queries to be executed.

Option 2: Use mysqli_result::fetch_all()

$result = mysqli_query($db, $sql);
$data = mysqli_fetch_all($result, MYSQLI_ASSOC);
// Execute subsequent queries

This returns the entire result set as an array, allowing multiple queries to be executed.

Consideration:

The nested queries indicate hierarchical data storage. Consider alternative data models or using frameworks like CodeIgnitor to handle multiple result sets from stored procedures using mysqli_next_result().

CodeIgnitor Implementation:

// Edit code in system/database/drivers/mysqli/mysqli_driver.php
protected function _execute($sql)
{
    $results = $this->conn_id->query($this->_prep_query($sql));
    @mysqli_next_result($this->conn_id); // Fix 'command out of sync' error
    return $results;
}

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