Using underscore (_) as a PHP function name

Question

According to http://php.net/manual/en/functions.user-defined.php, I should be able to use an underscore (_) as a function name:

Function names follow the same rules as other labels in PHP. A valid function name starts with a letter or underscore, followed by any number of letters, numbers, or underscores. As a regular expression, it would be expressed thus: [a-zA-Z_\x7f-\xff][a-zA-Z0-9_\x7f-\xff]*.

However, the following kills my program without causing any errors:

error_reporting(E_ALL);
echo('start');
function _($x){return ($x)?htmlspecialchars($x):'nbsp;';}
echo('end');

I am using PHP Version 5.3.18. What don't I understand?

If you had error reporting turned on, you would have seen an error about redeclaring _() — Tim
– Tim, Commented Dec 5, 2012 at 13:11

cmbuckley · Accepted Answer · 2012-12-05 13:08:54Z

17

There is already a built-in function called _; it is an alias for gettext.

You are likely getting a Fatal error: Cannot redeclare _(), but the error may not be output to your screen depending on your setting for display_errors. You could also look at the log_errors directive.

answered Dec 5, 2012 at 13:08

cmbuckley

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3 Comments

user1032531 Over a year ago

Thanks. Never knew that. Not documented very well: php.net/manual/en/function.gettext.php. Why isn't it throwing some sort of error?

Tim Over a year ago

@user1032531 It does: PHP Fatal error: Cannot redeclare _()

Mark Reed Over a year ago

You must have error reporting turned off. I get this output: PHP Fatal error: Cannot redeclare _() in foo.php on line 3

Shiplu Mokaddim · Accepted Answer · 2012-12-05 13:10:00Z

4

As cbuckley said, there is already a gettext alias defined with name _. If you have gettext enabled _ name is taken.

You better use double underscore (__). I use it frequently. Or you disable gettext.

answered Dec 5, 2012 at 13:10

Shiplu Mokaddim

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