[wp-trac] [WordPress Trac] #43619: Introduce new PHP cross-version compat function `is_iterable()`

[WordPress Trac]

#43619: Introduce new PHP cross-version compat function `is_iterable()`
-------------------------+-----------------------------
 Reporter:  jrf          |      Owner:
     Type:  enhancement  |     Status:  new
 Priority:  normal       |  Milestone:  Awaiting Review
Component:  General      |    Version:  trunk
 Severity:  normal       |   Keywords:
  Focuses:               |
-------------------------+-----------------------------
 Similar to and related to #43583

 PHP 7.2 introduced a warning when count() is used on something non-
 countable.

 PHP 7.1 introduced a new function called `is_iterable()` which basically
 checks:

 {{{#!php
 if (is_array($foo) || $foo instanceof Traversable) {
     // $foo is traversable
 }
 }}}


 See: http://php.net/manual/en/function.is-iterable.php


 When `count()` is used to check if an array is traverable, i.e. usable in
 a `foreach(){}`, it would be better to replace the `count()` check with a
 call to `is_iterable()`.


 To that end, I would like to suggest adding this new function to the `wp-
 includes/compat.php` file, like so:

 {{{#!php
 if ( ! function_exists( 'is_iterable' ) ) :
         function is_iterable( $var ) {
                 return ( ( is_array( $var ) && ! empty( $var ) || $var
 instanceof Traversable );
         }
 }
 endif;
 }}}


 This seems like low hanging fruit. Both the `instanceof` operator as well
 as the `Traversable` interface were already available in PHP 5.2.4, so
 there should be no cross-version compatibility issues with introducing
 this function.

 The function would provide an easy helper function to help fix the various
 issues where the warning is currently being reported - both for Core as
 well as for plugin/theme devs -.

 Existing code like this:

 {{{#!php
 if ( count( $var ) > 0 ) {
         foreach( $var as $key => $value) {
                 // Do something.
         }
 }
 }}}


 can then be replaced by:

 {{{#!php
 if ( is_iterable( $var ) ) {
         foreach( $var as $key => $value) {
                 // Do something.
         }
 }
 }}}


 The function would also still allow for code refactoring from arrays to
 objects. /cc @schlessera

 I would suggest introducing this function ASAP and not to wait for a major
 release.

 Related issues (there are probably more, but a quick search yielded
 these):
 #43583, #43374, #43368, #43312, #43216, #43201, #43216, #43201, #42860,
 #42814, #42147, #42498

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Ticket URL: <https://core.trac.wordpress.org/ticket/43619>
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