CheckBraceSyntax

<?
$start = microtime(true);



        function array_key_last($array) {
        if (!is_array($array) || empty($array)) {
            return NULL;
        }

        return array_keys($array)[count($array)-1];
    }

    function checkBraces($string){
        $arrPlus = array(
            '('=>1,
            '['=>2,
            '{'=>3,
            '<'=>4,
        );
        $arrMinus = array(
            ')'=>1,
            ']'=>2,
            '}'=>3,
            '>'=>4,
        );
        $reverseMinus = array(
            ')'=>'(',
            ']'=>'[',
            '}'=>'{',
            '>'=>'<',
        );
        $arPlus = ['(', '[', '{', '<'];
        $arMinus = [')', ']', '}', '>'];
        $strCount = strlen($string);
        $command = array();
        $j = 0;
        $i = 0;
        $curr = $string{1};
        while ($i <= $strCount) {
            $curr = $string{$i};
            if (in_array($curr,$arPlus)) {
                $j+=$arrPlus[$curr];
                $command[] = $curr;
            }
            if (in_array($curr,$arMinus)){
                if ($command){
                    if (end($command) !== $reverseMinus[$curr]) return 1;
                    if (($delete = end($command) == $reverseMinus[$curr])or end($command) == $curr){
                        $j-=$arrMinus[$curr];
                        if ($delete){
                            unset($command[array_key_last($command)]);
                            $delete = 0;
                        } else {
                            $command[] = $curr;
                        }
                    }
                } else {
                    return 1;
                }

            }
            $i++;
            //var_dump($i);
        }
        return ($j!==0)?1:0;
    }
    echo '<br>Тест #3: ' . checkBraces('before ( middle []) after ') . ' == 0<br>';

    echo '<br>Тест #1: ' . checkBraces('---(++++)----') . ' == 0<br>';
    echo '<br>Тест #2: ' . checkBraces('') . ' -> 0<br>';
    echo '<br>Тест #4: ' . checkBraces(') (') . ' == 1<br>';
    echo '<br>Тест #5: ' . checkBraces('} {') . ' == 1<br>';
    echo '<br>Тест #6: ' . checkBraces('<(   >') . ' == 1<br>';
    echo '<br>Тест #7: ' . checkBraces('(  [  <>  ()  ]  <>  )') . ' == 0<br>';
    echo '<br>Тест #8: ' . checkBraces('   (      [)') . ' == 1<br>';
    echo '<br>Тест #9: ' . checkBraces('[)') . ' == 1<br>';
    echo '<br>Тест #10: ' .checkBraces('({)}') . ' == 1<br>';
    echo '<br>Тест #11: ' .checkBraces('({') . ' == 1<br>';
    echo '<br>Время выполнения скрипта: ' . round(microtime(true) - $start, 8) . ' сек.';