PHP Defer

A defer statement originally comes from Golang. This library allows you to use defer functionality in PHP code.

Usage

<?php

defer($context, $callback);

go_defer($context, $callback);

defer and go_defer require two parameters: $context and $callback.

1. $context - unused in your app, required to achieve "defer" effect. I recommend to use $_ always.
2. $callback - a callback which is executed after the surrounding function returns.

defer executes callbacks First In, First Out. Functions execute in the order you deferred them.

go_defer more accurately emulates Golang's defer functionality and executes callbacks in Last In, First Out order.

Examples

Defer the execution of a code, using defer

<?php

function helloGoodbye()
{
    defer($_, function () {
        echo "...\n";
    });
    
    defer($_, function () {
        echo "goodbye\n";
    });

    echo "hello\n";
}

echo "before hello\n";
helloGoodbye();
echo "after goodbye\n";

// Output:
//
// before hello
// hello
// ...
// goodbye
// after goodbye

Defer the execution of a code, using go_defer

<?php

function rollCall()
{
    go_defer($_, function () {
        echo "I was deferred first!\n";
    });
    
    go_defer($_, function () {
        echo "I was deferred last!\n";
    });

    echo "I was NOT deferred!\n";
}

echo "before rollCall\n";
rollCall();
echo "after rollCall\n";

// Output:
//
// before rollCall
// I was NOT deferred!
// I was deferred last!
// I was deferred first!
// after rollCall

Defer and exceptions

<?php

function throwException()
{
    defer($_, function () {
        echo "after exception\n";
    });

    echo "before exception\n";

    throw new \Exception('My exception');
}

try {
    throwException();
} catch (\Exception $e) {
}

// Output:
//
// before exception
// after exception

Credits

This library is inspired by mostka/defer.