Issues related to performing mysqldump permissions

Permission issues to perform mysqldump
To make a backup of the entire database by clicking the button on the PHP page
$tmpname = "Wholesystem.sql";
Unlink ($setupdirection. "/tmp/$tmpname");
$command = "Mysqldump--opt--default-character-set=latin1-u $dbusername-P". $dbuserpass. "$dbnames >". $setupdirect Ion. "/tmp/$tmpname";
System ($command);
Download ($setupdirection. "/tmp/", $tmpname, $tmpname);

$command Print out the contents of the command line into the MySQL installation path under the bin, the execution succeeds!!
But with the above code, the output is always an empty SQL file
I know that the reason is that mysqldump executes directly on the command line, not internal commands, and must be executed under the bin of the MySQL installation path.

Do you want to save the MySQL installation path? The system transplant will be in trouble later.
Is there any other way to let $command run?

------Solution--------------------
Since the system porting, you should specify the full path, different systems, and even different installations will definitely put the command under different paths, including your destination directory, different systems certainly not the same.

It is recommended that you consider adding a SELECT into outfile with show create table and then using the load data infile.
------Solution--------------------
I don't know what that means upstairs.
How many times do I need to run?
In multiple databases?

mysqldump-uuser-ppass-h hostname databasename tablename1 tablename2 ...
This allows you to back up multiple tables.

