PHP Database Mysqli Connection issues

The PHP database mysqli connection issues.
I looked at the connection, the process, almost the same way as the Mysql-connect connection,

There's a question to ask.

It is said that mysql_connect connection is non-persistent, so you can generally omit to write Mysql_close ()

It is said that the Mysqli_connect connection is persistent, then you can omit to write Mysqli_close ()???
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Small white learning, using PDO to connect to the database
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Mysqli open a persistent connection to add p before the host name at connection time:
and MySQL has to use a specific function mysql_pconnect to achieve
So, it depends on whether you open a persistent or non-persistent connection to close it.

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