The expression return $commands; seems to be an array, but some of its elements' types (Pickle\Console\Command\V...mmand\SelfUpdateCommand) are incompatible with the return type of the parent method Symfony\Component\Consol...ion::getDefaultCommands of type array<Symfony\Component\...le\Command\ListCommand>.
If you return a value from a function or method, it should be a sub-type of the
type that is given by the parent type f.e. an interface, or abstract method.
This is more formally defined by the
Lizkov substitution principle,
and guarantees that classes that depend on the parent type can use any instance
of a child type interchangably. This principle also belongs to the
SOLID principles
for object oriented design.
Our function my_function expects a Post object, and outputs the author
of the post. The base class Post returns a simple string and outputting a
simple string will work just fine. However, the child class BlogPost which
is a sub-type of Post instead decided to return an object, and is
therefore violating the SOLID principles. If a BlogPost were passed to
my_function, PHP would not complain, but ultimately fail when executing the
strtoupper call in its body.
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44
}
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private static function checkExtensions()
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{
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$required_exts = array(
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"zlib",
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"mbstring",
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"simplexml",
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"json",
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"dom",
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"openssl",
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"phar",
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"zip",
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);
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foreach ($required_exts as $ext) {
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if (!extension_loaded($ext)) {
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die("Extension '$ext' required but not loaded, full required list: " . implode(", ", $required_exts));
The method checkExtensions() contains an exit expression.
An exit expression should only be used in rare cases. For example, if you
write a short command line script.
In most cases however, using an exit expression makes the code untestable
and often causes incompatibilities with other libraries. Thus, unless you are
absolutely sure it is required here, we recommend to refactor your code to
avoid its usage.
FriendsOfPHP /
pickle
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If you return a value from a function or method, it should be a sub-type of the type that is given by the parent type f.e. an interface, or abstract method. This is more formally defined by the Lizkov substitution principle, and guarantees that classes that depend on the parent type can use any instance of a child type interchangably. This principle also belongs to the SOLID principles for object oriented design.
Let’s take a look at an example:
Our function
my_functionexpects aPostobject, and outputs the author of the post. The base classPostreturns a simple string and outputting a simple string will work just fine. However, the child classBlogPostwhich is a sub-type ofPostinstead decided to return anobject, and is therefore violating the SOLID principles. If aBlogPostwere passed tomy_function, PHP would not complain, but ultimately fail when executing thestrtouppercall in its body.