Introducing new features from php7.3 to php7.4

1. Object attributes now support type declaration

<?php
class User {
    public int $id;
    public string $name;
}
?>

In the above example, $id will be forced to be converted to integer type, $name is String type

Recommended (free):PHP7

2. Arrow function

Now the arrow function will Provide a short syntax for defining functions whose value declarations are unclear within the scope

<?php
$factor = 10;
$nums = array_map(fn($n) => $n * $factor, [1, 2, 3, 4]);
// $nums = array(10, 20, 30, 40);
?>

3, limited return type covariance and parameter type covariance (Google Translate)

The following code will Will run

<?php
class A {}
class B extends A {}

class Producer {
    public function method(): A {}
}
class ChildProducer extends Producer {
    public function method(): B {}
}
?>

Full diff support is only provided when using autoloading. Within a single file, only non-cyclic type references can be used because all classes must be available before being referenced

4, Null merge assignment operator

<?php
$array[&#39;key&#39;] ??= computeDefault();
// is roughly equivalent to
if (!isset($array[&#39;key&#39;])) {
    $array[&#39;key&#39;] = computeDefault();
}
?>

5, Unpacking inside arrays (Google The translation is to unpack inside the array. See if this is wrong, use English first)

<?php
$parts = [&#39;apple&#39;, &#39;pear&#39;];
$fruits = [&#39;banana&#39;, &#39;orange&#39;, ...$parts, &#39;watermelon&#39;];
// [&#39;banana&#39;, &#39;orange&#39;, &#39;apple&#39;, &#39;pear&#39;, &#39;watermelon&#39;];
?>

6. Numeric character separator

Numeric characters can include underscores between numbers.

<?php
6.674_083e-11; // float
299_792_458;   // decimal
0xCAFE_F00D;   // hexadecimal
0b0101_1111;   // binary
?>

7. Weak references

Weak references allow the programmer to retain a reference to an object that cannot be prevented from being destroyed does not prevent the object from being destroyed.)

8. Allow exceptions __toString()

can now be thrown through __toString() Exceptions, which in previous versions would have resulted in a fatal error, existing string conversions that could have resulted in a fatal error have been converted to throw exceptions.

We will look at the rest of the expansion later

The above is the detailed content of Introducing new features from php7.3 to php7.4. For more information, please follow other related articles on the PHP Chinese website!