ShortArraySyntaxFixer.php

use Symfony\CS\FixerInterface;
use Symfony\CS\Tokens;

class ShortArraySyntaxFixer implements FixerInterface
{
    public function fix(\SplFileInfo $file, $content)
    {
        $tokens = Tokens::fromCode($content);

        for ($index = 0, $c = $tokens->count(); $index < $c; $index++) {
            $token = $tokens[$index];

            if (Tokens::isKeyword($token) && T_ARRAY === $token[0] && '(' === $tokens->getNextNonWhitespace($index)) {
                $this->fixArray($tokens, $index);
                continue;
            }
        }

        return $tokens->generateCode();
    }

    private function fixArray(Tokens $tokens, &$index)
    {
        $bracesLevel = 0;

        unset($tokens[$index]);
        $index++;

        for ($c = $tokens->count(); $index < $c; $index++) {
            $token = $tokens[$index];

            if ('(' === $token) {
                if (0 === $bracesLevel) {
                    $tokens[$index] = '[';
                }

                ++$bracesLevel;
                continue;
            }

            if (Tokens::isKeyword($token) && T_ARRAY === $token[0] && '(' === $tokens->getNextNonWhitespace($index)) {
                $this->fixArray($tokens, $index);
                continue;
            }

            if (')' === $token) {
                --$bracesLevel;

                if (0 === $bracesLevel) {
                    $tokens[$index] = ']';
                    break;
                }
            }
        }
    }

    public function getLevel()
    {
        return FixerInterface::ALL_LEVEL;
    }

    public function getPriority()
    {
        return 0;
    }

    public function supports(\SplFileInfo $file)
    {
        return 'php' === pathinfo($file->getFilename(), PATHINFO_EXTENSION);
    }

    public function getName()
    {
        return 'short_array_syntax';
    }

    public function getDescription()
    {
        return 'PHP array\'s should use the PHP 5.4 short-syntax';
    }
}

ShortArraySyntaxFixerTest.php

class ShortArraySyntaxFixerTest extends \PHPUnit_Framework_TestCase
{
    /**
     * @dataProvider provideExamples
     */
    public function testFix($expected, $input)
    {
        $fixer = new Fixer();
        $file = $this->getTestFile();

        $this->assertEquals($expected, $fixer->fix($file, $input));
    }

    public function provideExamples()
    {
        return array(
            array('<?php $x = [];', '<?php $x = array();'),
            array('<?php $x = []; $y = [];', '<?php $x = array(); $y = array();'),
            array('<?php $x = [ ];', '<?php $x = array( );'),
            array('<?php $x = [\'foo\'];', '<?php $x = array(\'foo\');'),
            array('<?php $x = [ \'foo\' ];', '<?php $x = array( \'foo\' );'),
            array('<?php $x = [($y ? true : false)];', '<?php $x = array(($y ? true : false));'),
            array('<?php $x = [($y ? [true] : [false])];', '<?php $x = array(($y ? array(true) : array(false)));'),//
            array('<?php $x = [($y ? [true] : [ false ])];', '<?php $x = array(($y ? array(true) : array( false )));'),
            array('<?php $x = [($y ? ["t" => true] : ["f" => false])];', '<?php $x = array(($y ? array("t" => true) : array("f" => false)));'),
            array('<?php print_r([($y ? true : false)]);', '<?php print_r(array(($y ? true : false)));'),
            array('<?php $x = [[[]]];', '<?php $x = array(array(array()));'),
            array('<?php $x = [[[]]]; $y = [[[]]];', '<?php $x = array(array(array())); $y = array(array(array()));'),
        );
    }

    private function getTestFile($filename = __FILE__)
    {
        static $files = array();

        if (!isset($files[$filename])) {
            $files[$filename] = new \SplFileInfo($filename);
        }

        return $files[$filename];
    }
}