Plugin Generated x Characters of Unexpected Output During Activation [Fix]

Updated on September 26, 2017

While developing a new plugin for WordPress, I ran into an error “Plugin Generated x Characters of Unexpected Output During Activation” when activated.

Here’s the complete error message:

The plugin generated 1825 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.


According to this blog, there are several reasons for this particular error. The author points out that the empty spaces above & after PHP open & close tags, file encoding issue and the usage of add_option in place of update_option might be the common reason for this error.

Based on the inputs from the above said blog, I tried to debug the issue and it was because of the missing PHP tags. What, Missing PHP tags? Yes. I know it was a silly mistake, but that’s what the reason behind the error. Due to the missing PHP tags, the server thinks it’s just a plain content that it needs to print it to the screen. So the plugin generated around 1825 characters of unexpected output to the screen.

If you are new to PHP development, then you are more likely to land up with silly errors as I did. PHP script without opening tag? I’m still stumped with that mistake.

As Greg Owen said, It was one of the silly mistake that I’ll be remembered for. At least, I will remember it!

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