How do Ruby and PHP differ in their evaluation mechanisms?

PHP / empty

is pretty much the same as Ruby equivalent.For empty?

strings in Rails, the method is blank?

preferredempty?

# this is PHP
$bob = array();          # empty( $bob ) => true
$bob = array( "cat" );   # empty( $bob ) => false

$bob = null;        # empty( $bob ) => true
$bob = "boo"        # empty( $bob ) => false
$bob = "";          # empty( $bob ) => true

# this is Ruby
[].empty?           # => true
[ "cat" ].empty?    # => false

nil.empty?          # => NoMethodError
"boo".empty?        # => false
"".empty?           # => true

      

        
        
        
      

    

PHP / isset can be replaced with has_key? for the Hash object. For general use of a local variable, Ruby creates variables as nil when they reference code, so the only simple check is whether or not they are nil?

EDIT

You can also use a keyword defined?

to duplicate PHP usage isset

for local variables.

#PHP

isset($bob);        # => false
$bob = "foo";
isset($bob);        # => true

$bob =  array();
isset($bob['cat']);  # => false

$bob =  array( 'cat' => 'bag' );
isset($bob['cat']);  # => true
isset($bob['dog']);  # => false

#Ruby
bob                  # => nil
defined?(bob)        # => false
bob.nil?             # => true
bob = "foo"
bob                  # => "foo"
bob.nil?             # => "false"
bob = {}
bob.has_key? :cat    # => false
bob = { :cat => 'bag' }
bob.has_key? :cat    # => true

      

        
        
        
      

    

One note: in PHP, an empty string or a numeric value of 0 will evaluate to false in the statement if

. In Ruby, only nil

and false

evaluates to false in an if statement. This requires adding two more Boolean query methods blank?

and zero?

. These methods are mixed with the String class as part of the Rails application. Free versions of these can be found on Facets.