PHP Warning missing Argument 1 for __()

Question

I am getting this error in my server error logs:

[Thu Dec 11 10:06:30 2014] [error] [client 11.111.111.111] PHP Warning:  Missing argument 1 for __(), called in /var/www/vhosts/mysite.org/public_html/wp-content/themes/mysite_v2.2/functions-cpt-projects.php on line 15 and defined in /var/www/vhosts/mysite.org/public_html/wp-includes/l10n.php on line 146, referer: http://www.mysite.org/wp-admin/edit.php

I've never encountered this before and I'm wondering what might be causing it. The line of code it refers to in the l10n.php file is:

function __( $text, $domain = 'default' ) {
    return translate( $text, $domain );
}

I'm wondering if anyone knows how I might go about debugging this? I read somewhere that it could be related to a plugin and to disable them one by one to find out if the issue is resolved but this has not worked for me as of yet.

Answer 1

you get this error if you passed empty string or did not pass any argument to the __() function.

You should check where you've used the __() function and check what value is being passed as argument.

Answer 2

I had a similar problem.
The issue was with a Custom Post Type and the solution was that the _x() translation function needed context (the 'missing argument') for a single word that has multiple meanings.

Example: Custom Post Type "Members" threw this error:

Warning: Missing argument 2 for _x(), called in /wp-content/plugins/my-cpt/posttypes.php on line 29 and defined in /Users/SITE-NAME/Sites/THEME-NAME/wp-includes/l10n.php on line 294

---

Without context, my Custom Post Type looked like this:

---

The 'Members' name/s were throwing all the errors because without context, (the second argument taken by the _x() function), translators might not know which Member I was referring to.

---

For Example:

• Member - Someone or something that belongs to a group or an organization?
• Member - A part of a structure?
• Member - A body part, such as an arm or a leg?
  
  

  ---

  So I added context:

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And the error messages went away.