mysqldump via PHP

Question

I have a PHP script that gets passed the MySQL connection details of a remote server and I want it to execute a mysqldump command. To do this I'm using the php exec() function:

<?php
exec("/usr/bin/mysqldump -u mysql-user -h 123.145.167.189 -pmysql-pass database_name > /path-to-export/file.sql", $output);
?>

When the right login details are passed to it, it'll work absolutely fine. However, I'm having trouble checking if it executes as expected and if it doesn't finding out why not. The $output array returns as empty, whereas if I run the command directly on the command line a message is printed out telling me the login failed. I want to capture such error messages and display them. Any ideas on how to do that?

Answer 1

You should check the third parameter of exec function: &$return_var.

$return_var = NULL;
$output = NULL;
$command = "/usr/bin/mysqldump -u mysql-user -h 123.145.167.189 -pmysql-pass database_name > /path-to-export/file.sql";
exec($command, $output, $return_var);

By convention in Unix a process returns anything other than 0 when something goes wrong.

And so you can:

if($return_var) { /* there was an error code: $return_var, see the $output */ }

Answer 2

The solution I found is to run the command in a sub-shell and then output the stderr to stdout (2>&1). This way, the $output variable is populated with the error message (if any).

i.e. :

exec("(mysqldump -uroot -p123456 my_database table_name > /path/to/dump.sql) 2>&1", $output, $exit_status);

var_dump($exit_status); // (int) The exit status of the command (0 for success, > 0 for errors)
echo "<br />";
var_dump($output); // (array) If exit status != 0 this will handle the error message. 

Results :

int(6)

array(1) { [0]=> string(46) "mysqldump: Couldn't find table: "table_name"" }

Hope it helps !

Answer 3

Because this line redirect the stdout output > /path-to-export/file.sql try this,

<?php 
exec("/usr/bin/mysqldump -u mysql-user -h 123.145.167.189 -pmysql-pass database_name", $output);
/* $output will have sql backup, then save file with these codes */
$h=fopen("/path-to-export/file.sql", "w+");
fputs($h, $output);
fclose($h);
?> 

Answer 4

I was looking for the exact same solution, and I remembered I'd already solved this a couple of years ago, but forgotten about it.

As this page is high in Google for the question, here's how I did it:

<?php
define("BACKUP_PATH", "/full/path/to/backup/folder/with/trailing/slash/");

$server_name   = "your.server.here";
$username      = "your_username";
$password      = "your_password";
$database_name = "your_database_name";
$date_string   = date("Ymd");

$cmd = "mysqldump --hex-blob --routines --skip-lock-tables --log-error=mysqldump_error.log -h {$server_name} -u {$username} -p{$password} {$database_name} > " . BACKUP_PATH . "{$date_string}_{$database_name}.sql";

$arr_out = array();
unset($return);

exec($cmd, $arr_out, $return);

if($return !== 0) {
    echo "mysqldump for {$server_name} : {$database_name} failed with a return code of {$return}\n\n";
    echo "Error message was:\n";
    $file = escapeshellarg("mysqldump_error.log");
    $message = `tail -n 1 $file`;
    echo "- $message\n\n";
}
?>

It's the --log-error=[/path/to/error/log/file] part of mysqldump that I always forget about!

Answer 5

As exec() is fetching just stdout which is redirected to the file, we have partial or missing result in the file and we don't know why. We have to get message from stderr and exec() can't do that. There are several solutions, all has been already found so this is just a summary.

1. Solution from Jon: log errors from mysqldump and handle them separately (can't apply for every command).
2. Redirect outputs to separate files, i.e. mysqldump ... 2> error.log 1> dump.sql and read the error log separately as in previous solution.
3. Solution from JazZ: write the dump as a subshell and redirect stderr of the subshell to stdout which can php exec() put in the $output variable.
4. Solution from Pascal: better be using proc_open() instead of exec() because we can get stdout and stderr separately (directly from pipes).

Answer 6

write below code to get the database export in .sql file.

<?php exec('mysqldump --user=name_user --password=password_enter --host=localhost database_name > filenameofsql.sql'); ?>