what does exec() return here? - php

Question

Following is a query string to import database:
$query = "mysql --user" . $this->userName . " --password " . $this->DatabaseName . " < " . $completePathOfSQLFile;
$resultQuery = exec($query);
The command executes fine. But what does exec function return? I need to make sure that the operation was performed correctly and return true | false accordingly.

Answer 1

From the manual
Return Values
The last line from the result of the command.
But note that you can also pass a third argument to exec which will be the return status of the command. Non-zero values are usually error states, the mysql client may use that sensibly. The manual has notes on various other approaches too, it's worth reading.

Answer 2

As Quentin said 3rd parameter of exec is return_var
string exec ( string $command [, array &$output [, int &$return_var ]] )
mysql will return non-zero exit code in case of an error.
# mysql -u root -e "SELECT 1" > /dev/null 2>&1
# echo $?
0 <- returns 0 for success
# mysql -u root -e "SOMETHING WRONG" > /dev/null 2>&1
# echo $?
1 <- Wrong statement
Please note that if the file is empty , it will still return "0", since there is no SQL syntax error or wrong arguments given to mysql client.
So You can add this to your code :
$query = "mysql --user" . $this->userName . " --password " . $this >DatabaseName . " < " . $completePathOfSQLFile;
$resultQuery = exec($query,$output,$return_var);
if (intval($return_var) !== 0) {
echo "error: ".$output;
}