Short and safe array traversal in PHP

When writing PHP array traversal, we usually write like this:

foreach ($definition['keys'] as $id => $val) {
  // ...
}

But in fact this will cause an important problem: if $definition['keys '] If it is not defined, an error will occur in the array variable (that is, foreach) at this time.

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So, we have advanced to this:

if (!empty($definition['keys']) {
  foreach ($definition['keys'] as $id => $val) {
    // ...
  }
}

Is it very common? We just need to include another layer of if judgments outside. This ensures safe array traversal.

However, this does not meet the brief requirement, so with the convenience of PHP7, we can write it like this:

foreach ($definition['keys'] ?? [] as $id => $val) {
  // ...
}

Isn’t it very neat! Hahaha, then understand here?? It can be understood this way:

$a = is_null($b) ? $default : $b;
$a = $b ?? $default;

is equivalent to doing an is_null($b) operation.

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