PHP7+ also supports type declarations. Let's talk about this feature!

PHP has also begun to engage in type declarations. PHP7 has added the feature of type declaration. The following article will take you to understand the features of PHP type declaration and share the pitfalls in return type declaration. I hope it will be helpful to everyone!

Recently I have been studying the new features of PHP7 and found that PHP has also begun to use type declarations. The benefits of doing so are obvious: it can improve the running speed of the program.

Let’s start with the introduction of this new feature:

By default, all PHP files are in weak type checking mode.

PHP7 has added the feature of type declaration. There are two modes for type declaration:

• Force mode (default mode) My understanding is to force conversion to required The type is not strictly differentiated but forced to be converted. If the type is inconsistent, no error will be reported
• Strict mode Strictly verify the type. If the type is inconsistent with the declared one, an error will be reported

Scalar type declaration syntax format:

declare(strict_types=1);

The value of strict_types:

• 1 indicates strict type checking mode, which applies to function calls and return statements;
• 0 indicates weak type checking mode

The type parameters that can be used are:

• string
• int
• float
• bool
• interfaces
• array
• callable

Force mode (default mode)

<?php

function sum(int ...$ints)
{
   return array_sum($ints);
}

print(sum(1, &#39;2&#39;, 3.1));
?>

The execution output of the above program is: 6

Analysis: Convert string type '2' into integer type 2 , convert the float type 3.1 into the integer type 3 and then add them together to get the result 6.

Strict Mode

<?php

declare(strict_types=1);

function sum(int ...$ints)
{
   return array_sum($ints);
}

print(sum(1, &#39;2&#39;, 3.1));
?>

The above program uses strict mode and because the second parameter is not of int type, the execution result is as follows:

PHP Fatal error: Uncaught TypeError: Argument 2 passed to sum() must be of the type integer, string given, called in……

Return type declaration

PHP7 adds support for return type declaration, which specifies the type of function return value.

The return types that can be declared are:

• string
• int
• float
• bool
• interfaces
• array
• callable

The pit I stepped on

I really am here After going through the pit, in the new version of phpstorm, a prompt code will appear according to the return value type, guiding you to add a return type declaration, so I added it. But later due to business changes or code optimization, I only modified the return value (for example, I returned array before, but after the modification, I returned int), but I forgot to modify the return type declaration (after all, I have been used to PHP's weak language types for so many years... ), this will throw an exception and cause an error. This is the pitfall I stepped on. Guys, please pay attention when using it.

Thinking

GO language will not have the problem I mentioned above, because if the return value type and return type declaration If the compilation fails, an error will be reported during compilation.

As a weakly typed language, PHP has made optimizations such as return type declarations, but it does not require us to compile before the language is executed. It can be released and run directly, so it cannot achieve the Go language. "Compilation alarm" occurs, PHP will throw an exception directly during execution.

<?php
declare(strict_types=1);

function returnIntValue(int $value): int
{
   return $value;
}

print(returnIntValue(5));
?>

The execution output of the above program is: 5

Return type declaration error example

<?php
declare(strict_types=1);

function returnIntValue(int $value): int
{
   return $value + 3.0;
}

print(returnIntValue(1));
?>

Because the above program adopts strict mode, the return value must be int, but the calculation result is float, resulting in an error. The execution output result is: Fatal error: Uncaught TypeError: Return value of returnIntValue() must be of the type integer, float returned...

void function

Note: Define a function with a return type of void There cannot be a return value, even if it returns null.

Methods whose return value is declared as void type either simply omit the return statement or use an empty return statement.

Example

<?php
function exchange(&$left, &$right) : void
{
    if ($left === $right) {
        return;
    }

    $tmp = $left;
    $left = $right;
    $right = $tmp;
}

$a = 1;
$b = 2;
var_dump(exchange($a, $b), $a, $b);

The above example output result:

null int(2) int(1)

Original address: https://juejin.cn/post/7062942459247984648

Author: Wang Zhongyang Go

Recommended learning: "PHP Video Tutorial》

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