Does setting a PDO connection to NULL truly close the connection and free up resources?

Closing PDO Connections

In PHP, there are two popular database connection interfaces: MySQLi and PDO. While both serve similar purposes, they handle connection closing differently.

MySQLi requires an explicit close function call to release the connection:

<code class="php">$this->connection->close();</code>

In contrast, PDO uses a null assignment to terminate the connection:

<code class="php">$this->connection = null;</code>

This distinction raises questions about the effectiveness of PDO's approach. Will setting the connection to null truly free up resources?

PDO Connection Life Cycle

According to the PDO documentation, the connection remains active for the lifetime of the PDO object. To close it, one must destroy the object by assigning NULL to the variable holding it.

Automatic Connection Closure

If the user neglects to close the connection explicitly, PHP will automatically do so when the script ends. However, this behavior changes if the PDO object is initialized as a persistent connection. In that case, the connection will not close automatically and must be terminated manually.

Conclusion

Setting a PDO connection to NULL is an effective way to release resources and close the connection. However, it's important to note that persistent connections may require additional attention for proper closure.

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