Why can't a backup of a database table be done via shell_exec?

Question

PHP

I make a backup of the database table with the command
mysqldump -u dbuser -pdbPassword dbName tableName | gzip > `date +{$rootDir}_service/dbbackups/$folder/tableName .%Y-%m-%d.%H-%M-%S.sql.gz`
If I run the command in the console, everything is fine, but if I run the command through shell_exec, then the archive is created with a size of 20 bytes. this is clearly not a complete archive. Why doesn't it work through shell_exec, what are the possible reasons?

Answer 1

conveyor is not working. Because it is provided by the shell (/bin/bash and the like) and you run the command without it.

Answer 2

Clarification: even when I run the php script itself through the console, everything is fine, but when this script is run through the browser, mysqldump creates an empty file, and if you use gzip compression, then the file is 20B in size