Tom Auger Tom Auger - 7 months ago 6
Perl Question

Best way to give a variable a default value (simulate Perl ||, ||= )

I love doing this sort of thing in Perl:

$foo = $bar || $baz
to assign
$baz
to
$foo
if
$bar
is empty or undefined. You also have
$foo ||= $bletch
which will only assign
$bletch
to
$foo
if
$foo
is not defined or empty.

The ternary operator in this situation is tedious and tiresome. Surely there's a simple, elegant method available in PHP?

Or is the only answer a custom function that uses isset()?

Answer

PHP 5.3 has a shorthand ?: operator:

$foo = $bar ?: $baz;

Which assigns $bar if it's not an empty value (I don't know how this would be different in PHP from Perl), otherwise $baz, and is the same as this in Perl and older versions of PHP:

$foo = $bar ? $bar : $baz;

But PHP does not have a compound assignment operator for this (that is, no equivalent of Perl's ||=).

Also, PHP will make noise if $bar isn't set unless you turn notices off. There is also a semantic difference between isset() and empty(). The former returns false if the variable doesn't exist, or is set to NULL. The latter returns true if it doesn't exist, or is set to 0, '', false or NULL.