如何通过正则表达式匹配多个括号外的逗号

Question

我用逗号分割了一个字符串，但不是在括号内，使用 preg_split。我想到了

preg_split('#,(?![^\(]*[\)])#',$str);

除非嵌套括号前有逗号，否则效果很好。

适用于

$str = "first (1,2),second (child (nested), child2), third";

Array
(
    [0] => first (1,2)
    [1] => second (child (nested), child2)
    [2] =>  third
)

但不适用于

$str = "first (1,2),second (child, (nested), child2), third";

Array
(
    [0] => first (1,2)
    [1] => second (child
    [2] =>  (nested), child2)
    [3] =>  third
)

Answer 1

看看忽略括号内的,的要求，这个问题归结为确保括号平衡。如果任何 , 位于 不平衡括号 内，我们将忽略它们，否则 , 现在是我们拆分的分隔符。

为了收集这些 , 之间的字符串，我们维护一个起始指针 $sub_start 来跟踪子字符串的起始索引，并在我们遇到有效的分隔符后更新它们 ,.

片段：

<?php

function splitCommaBased($str){
    $open_brac = 0;
    $len = strlen($str);
    $res = [];
    $sub_start = 0;
    
    for($i = 0; $i < $len; ++$i){
        if($str[ $i ] == ',' && $open_brac == 0){
            $res[] = substr($str, $sub_start, $i - $sub_start);
            $sub_start = $i + 1;
        }else if($str[ $i ] == '('){
            $open_brac++;
        }else if($str[ $i ] == ')'){
            $open_brac--;
        }else if($i === $len - 1){
            $res[] = substr($str, $sub_start);
        }
    }
    
    return $res;
}

print_r(splitCommaBased('first (1,2),second (child, (nested), child2), third'));

Answer 2

你可以使用匹配平衡括号的递归。然后使用 SKIP FAIL 并匹配要拆分的逗号。

(\((?:[^()]++|(?1))*\))(*SKIP)(*F)|,

看到一个regex demo。

例子

$str = "first (1,2),second (child, (nested), child2), third";
$pattern = "/(\((?:[^()]++|(?1))*\))(*SKIP)(*F)|,/";
print_r(preg_split($pattern, $str));

输出

Array
(
    [0] => first (1,2)
    [1] => second (child, (nested), child2)
    [2] =>  third
)

如何通过正则表达式匹配多个括号外的逗号

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