Excerpt of new features in PHP version - php7.1x

This article excerpts from php.net

1. May be empty （Nullable） type

Parameters and the type of the return value can now be allowed to be empty by prefixing the type with a question mark . When this feature is enabled , The result returned by the passed parameter or function is either of the given type , Or null .

<?php
    
    function testReturn(): ?string
    {
    
        return 'elePHPant';
    }

    var_dump(testReturn());

    function testReturn(): ?string
    {
    
        return null;
    }

    var_dump(testReturn());

    function test(?string $name)
    {
    
        var_dump($name);
    }

    test('elePHPant');
    test(null);
    test();

The above routine will output

string(10) "elePHPant"
NULL
string(10) "elePHPant"
NULL
Uncaught Error: Too few arguments to function test(), 0 passed in...

2. Class constant visibility

<?php

class ConstDemo
{
    
    const PUBLIC_CONST_A = 1;
    public const PUBLIC_CONST_B = 2;
    protected const PROTECTED_CONST = 3;
    private const PRIVATE_CONST = 4;
}

3. Symmetric array destructuring

Short array syntax （[]） Now as list() An alternative to syntax , It can be used to assign the value of the array to some variables （ Included in foreach in ）.

<?php
    $data = [
    	[1, 'Tom'],
    	[2, 'Fred'],
    ];

    // list() style
    list($id1, $name1) = $data[0];

    // [] style
    [$id1, $name1] = $data[0];

    // list() style
    foreach ($data as list($id, $name)) {
    
        // logic here with $id and $name
    }

    // [] style
    foreach ($data as [$id, $name]) {
    
        // logic here with $id and $name
    }

4. list() Key names are now supported

Now? list() And its new [] Syntax supports specifying key names within it . This means that it can put any type of array All assigned to variables （ Similar to short array syntax ）

<?php
    $data = [
        ["id" => 1, "name" => 'Tom'],
        ["id" => 2, "name" => 'Fred'],
    ];

    // list() style
    list("id" => $id1, "name" => $name1) = $data[0];

    // [] style
    ["id" => $id1, "name" => $name1] = $data[0];

    // list() style
    foreach ($data as list("id" => $id, "name" => $name)) {
    
        // logic here with $id and $name
    }

    // [] style
    foreach ($data as ["id" => $id, "name" => $name]) {
    
        // logic here with $id and $name
    }

5. Support negative string offsets

Now all of the String manipulation functions Both support accepting negative numbers as offsets , Including passage [] or {} operation String subscript . under these circumstances , A negative offset is interpreted as an offset starting at the end of the string .

use Operator It has been extended to support importing external functions and constants in classes . The corresponding structure is use function and use const.

<?php
	var_dump("abcdef"[-2]);
	var_dump(strpos("aabbcc", "b", -3));

    $string = 'bar';
	echo "The last character of '$string' is '$string[-1]'.\n";

The above routine will output

string (1) "e"
int(3)
The last character of 'bar' is 'r'.