MySQLdump empty file using PHP but not command line?

Question

I'm playing around with a backup script for mysql. A variation of this used to work, but I haven't looked at it since php4. It's returning an empty file. The weird thing is that if I go to the command line and use the EXACT same command, I get the file I'm expecting.

I've poked around the internet and can't find anything... thoughts?

Bad code?

$db_host='localhost';
$db_user='root';
$db_pass='root';
$db_name='gakkou';
$dir='backups';
$file_list=scandir($dir);
if(count($file_list)>10) unlink($dir.'/'.$file_list[2]); //delete old file
$prefix=date("YmdHi").'_';
$command='mysqldump -u'.$db_user.' --password="'.$db_pass.'" --databases '.$db_name.' | gzip > '.$dir.'/'.$prefix.'_backup.sql.gzip';
exec($command,$output,$return_val);

This works perfectly: mysqldump -uroot -proot -hlocalhost gakkou > /webdocs/gakkou/backups/mysql_backup.sql and it is exactly the same as the command the php file executes (except for the file name).

EDIT: updated with working code for anyone interested. This turned out to be two separate issues. Using MAMP, I needed to specify the path /Applications/MAMP/Library/bin/mysqldump. Then on the production server the crazy password gummed up the works.

is mysqldump in the path of whatever shell PHP's using? try a fullblown /usr/bin/mysqldump or whatever the absolute path is on your system. Plus, if it's failing, exec($command, $output, $return_val); var_dump($output, $return_val) will probably have some debug output useful for tracking down the problem. — Marc B
– Marc B, Commented Mar 2, 2014 at 4:07
Thanks, Marc. Absolute path seems to have done the trick on my development machine, but it still fails on the real deal. array(4) { [0]=> string(44) "Usage: mysqldump [OPTIONS] database [tables]" [1]=> string(65) "OR mysqldump [OPTIONS] --databases [OPTIONS] DB1 [DB2 DB3...]" [2]=> string(52) "OR mysqldump [OPTIONS] --all-databases [OPTIONS]" [3]=> string(38) "For more options, use mysqldump --help" } int(127) — jonlink
– jonlink, Commented Mar 2, 2014 at 4:33
The above seems to imply that the command I'm executing is bad, but when I echo it out I get what I'd expect mysqldump -uUSER -pPASSWORD -hlocalhost DB_NAME > backups/23-20140301_gakkou_backup.sql — jonlink
– jonlink, Commented Mar 2, 2014 at 5:02
OK. FINALLY got it figured out. My super stupid password was messing with mysqldump because it had an "&" in it. Didn't have to change the password. I just enclosed the password in parentheses: --password="'.$db_pass.'" Now it works as expected. So many hours wasted... @MarcB, thank you so much for your help. Didn't know how to return the errors and that was definitely the biggest roadblock. — jonlink
– jonlink, Commented Mar 2, 2014 at 15:38

jonlink · Accepted Answer · 2014-06-10 05:48:11Z

5

OK. FINALLY got it figured out. My super stupid password was messing with mysqldump because it had an "&" in it. Didn't have to change the password. I just enclosed the password in parentheses: --password="'.$db_pass.'" Now it works as expected. So many hours wasted... @MarcB, thank you so much for your help. Didn't know how to return the errors and that was definitely the biggest roadblock.

answered Jun 10, 2014 at 5:48

jonlink

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2 Comments

jonlink Over a year ago

@shi, comment is now answer! :)

Simone Over a year ago

You saved my day :) :). was struggling with this for so long thinking that it is an error in the syntax

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