Double underscore in PHP

Question

What does the double underscores in these lines of PHP code mean?

$WPLD_Trans['Yes'] = __('Yes', $WPLD_Domain);
$WPLD_Trans['No'] = __('No', $WPLD_Domain);

Given [the accepted answer](https://stackoverflow.com/questions/1777131/double-underscore-in-php/1777147#1777147), related: *[Why double underscore (__) in PHP function names?](https://stackoverflow.com/questions/5348663/why-double-underscore-in-php)* — Peter Mortensen, Feb 23 '22 at 14:29

score 70 · Accepted Answer · edited Feb 23 '22 at 13:57

70

It looks like you're using WordPress - wp-includes/l10n.php defines __ as a function that translates a string (similar to gettext and its alias, _, but with an optional parameter for explicitly specifying a domain).

edited Feb 23 '22 at 13:57

Peter Mortensen

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answered Nov 21 '09 at 23:33

SimonJ

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Hideous, but very convenient. As a sidenote, php.net says that all functions starting with __ (double underscore) are reserved. It sounds like they don't like the fact that WordPress and others are poaching on their magic method territory. http://us.php.net/manual/en/language.oop5.magic.php – Lane Feb 20 '12 at 18:52
Based on this, it sounds like I can get rid of this if no translation is required. Is this correct? E.g., $WPLD_Trans['Yes'] = 'Yes'; – Randy Greencorn Nov 12 '14 at 17:32

score 42 · Answer 2 · answered Nov 21 '09 at 23:30

42

Strictly speaking, it means nothing in PHP as it is not a pre-defined function. However, in many frameworks, like CakePHP, and other libraries the double underscore is a function used for translating strings based on the user's language/locale preference.

answered Nov 21 '09 at 23:30

Mike B

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No idea. Confusingly though, the CakePHP version of __ behaves completely differently to the one in Wordpress (CakePHP, by default, echoes the string unless the second parameter is false). I'll bet *that* never tripped anybody up before... – SimonJ Nov 22 '09 at 02:01

score 9 · Answer 3 · edited Feb 23 '22 at 14:14

9

WordPress documents its __() function, and part of the localisation technology on Working with WordPress Core – Translate WordPress.

It is difficult to find documentation because __(), __('') or __("") is not very searchable. Double underscore and parentheses (round brackets) are some keywords to use.

edited Feb 23 '22 at 14:14

Peter Mortensen

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answered Jan 17 '15 at 21:04

PaulH

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score 6 · Answer 4 · answered Nov 21 '09 at 23:37

6

As mentioned it is generally used for translating text between languages but really it is used in the same context as any function call.

testfunction();

is no different then

__();

answered Nov 21 '09 at 23:37

JasonDavis

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Actually, testfunction() is very different, because it has a sane name. __ is a completely stupid thing to name a function. – J. Taylor Apr 13 '11 at 07:30

score 2 · Answer 5 · edited Feb 23 '22 at 14:12

2

A similar or third-party GNU gettext based implementation is gettext():

Note: You may use the underscore character '_' as an alias to this function.

edited Feb 23 '22 at 14:12

Peter Mortensen

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answered Nov 21 '09 at 23:49

knoopx

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How does that answer the question? – Peter Mortensen Feb 23 '22 at 14:11
From [an answer](https://stackoverflow.com/questions/10047766/php-what-are-these-underscores/10047789#10047789) to another question: *"A single underscore is an alias to gettext()."* – Peter Mortensen Feb 23 '22 at 14:54

Double underscore in PHP

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