Is mysql_close necessary because HTTP is a stateless protocol?

Since HTTP is a stateless protocol, is mysql_close necessary? Since the connection is checked once, why do we need to close the connection? There is also an imagedestroy function to release the memory for uploading images. if I do not release the image, will the machine memory remain silly and occupy the image until it crashes ?, Since HTTP is a stateless protocol, is mysql_close necessary?
Since the connection is checked once, why do we need to close the connection?

There is also an imagedestroy function to release the memory for uploading images. if I do not release the image, will the machine memory remain silly and occupy the image until it crashes?
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The connection between your website visitor (his computer or mobile phone) and your web server (such as apache) is http,

Mysql_connect establishes a connection between your web server and your mysql server (even if they are on a machine)

If you forget to close the database connection, the connection will be retained until you close the connection or the php running of the request is completed...

If you do not have imagedestroy, the memory will be occupied until you destroy or the operation ends. (I am not sure if it will be reclaimed, if the number of resources referenced in the image is 0)