PHP Macros for Fun and Profit!

Use the Yay preprocessor library to add syntax sugar to PHP to easily implement more elegant code! This article will demonstrate how to use the Yay library to add Ruby-like array slice syntax sugar for PHP. $many[4..8]

Core points:

Yay is a preprocessor library that allows developers to add syntactic sugar to other languages ​​to PHP through macros.
Yay breaks the code string into tags, builds an abstract syntax tree (AST), then replaces the macro element with real PHP code, and reassembles the PHP code.
While there are some limitations in variable scope and parser, Yay still allows for the creation of cleaner and more efficient PHP code.

Many PHP developers come from other programming language backgrounds and are used to some concise syntax in other languages. Yay library was created to solve this problem. For example, in Ruby, we can use

to get the second, third, and fourth elements of an array few = many[1..3]. And in PHP, we need to use many to achieve the same function. Obviously, Ruby's syntax is more concise and elegant. $few = array_slice($many, 1, 3);

Get to use macros:

First of all, we need to install the Yay library:

<code class="language-bash">$ composer require yay/yay:dev-master</code>

Next, we create a file called

with the following code: array_slice.yphp

<code class="language-php">macro {
    T_VARIABLE·A[
        ···range
    ]
} >> {
    eval(
        '$list = ' . →(T_VARIABLE·A) . ';' .
        '$lower = ' . explode('..', →(···range))[0] . ';' .
        '$upper = ' . explode('..', →(···range))[1] . ';' .
        'return array_slice($list, $lower, $upper - $lower);'
    )
}

macro {
    →(···expression)
} >> {
    ··stringify(···expression)
}


$many = [
    "She walks in beauty",
    "like the night",
    "of cloudless climes",
    "and starry skies",
    "And all that's best",
    "of dark and bright",
    "meet in her aspect",
    "and her eyes",
    "...",
];

$lower = 4;
$upper = 8;

$few = $many[$lower..$upper];
</code>

Then, use the Yay compiler to convert the

file to standard PHP code: .yphp

<code class="language-bash">$ vendor/bin/yay array_slice.yphp >> array_slice.php</code>

The generated

file will contain the following (may differ slightly, depending on the Yay version): array_slice.php

<code class="language-php">$many = [
    "She walks in beauty",
    "like the night",
    "of cloudless climes",
    "and starry skies",
    "And all that's best",
    "of dark and bright",
    "meet in her aspect",
    "and her eyes",
    "...",
];

$lower = 4;
$upper = 8;

$few = eval(
    '$list = ' . '$many' . ';'.
    '$lower = ' . explode('..', '$lower..$upper')[0] . ';' .
    '$upper = ' . explode('..', '$lower..$upper')[1] . ';' .
    'return array_slice($list, $lower, $upper - $lower);'
);</code>

Working principle:

Yay breaks the code string into tags through a parser, builds an abstract syntax tree (AST), and replaces the macro with real PHP code, and eventually generates executable PHP code. Due to the limitations of the scope of PHP variables, the macro uses the

function, which is slightly inelegant, but effectively implements the expected functions. eval()

With Yay, we can add custom syntax sugar to PHP, improving the readability and efficiency of our code. If you have more ideas or suggestions about the Yay library, please leave a message to discuss.

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