我创建了这个小函数，用limit替换字符串上的字符串(区分大小写)，而不需要Regexp。它工作得很好。

function str_replace_limit($search, $replace, $string, $limit = 1) {
    $pos = strpos($string, $search);

    if ($pos === false) {
        return $string;
    }

    $searchLen = strlen($search);

    for ($i = 0; $i < $limit; $i++) {
        $string = substr_replace($string, $replace, $pos, $searchLen);

        $pos = strpos($string, $search);

        if ($pos === false) {
            break;
        }
    }

    return $string;
}

使用示例:

$search  = 'foo';
$replace = 'bar';
$string  = 'foo wizard makes foo brew for evil foo and jack';
$limit   = 2;

$replaced = str_replace_limit($search, $replace, $string, $limit);

echo $replaced;
// bar wizard makes bar brew for evil foo and jack

function str_replace_once($search, $replace, $subject) {
    $pos = strpos($subject, $search);
    if ($pos === false) {
        return $subject;
    }

    return substr($subject, 0, $pos) . $replace . substr($subject, $pos + strlen($search));
}

可以用preg_replace完成:

function str_replace_first($search, $replace, $subject)
{
    $search = '/'.preg_quote($search, '/').'/';
    return preg_replace($search, $replace, $subject, 1);
}

echo str_replace_first('abc', '123', 'abcdef abcdef abcdef'); 
// outputs '123def abcdef abcdef'

神奇之处在于可选的第四个参数[Limit]。从文档中可以看到:

[极限]-最大可能 每个中的每个模式的替换 主题字符串。默认为-1 (no 限制)。

不过，请参阅zombat的回答以获得更有效的方法(大约快3-4倍)。

我创建了这个小函数，用limit替换字符串上的字符串(区分大小写)，而不需要Regexp。它工作得很好。

function str_replace_limit($search, $replace, $string, $limit = 1) {
    $pos = strpos($string, $search);

    if ($pos === false) {
        return $string;
    }

    $searchLen = strlen($search);

    for ($i = 0; $i < $limit; $i++) {
        $string = substr_replace($string, $replace, $pos, $searchLen);

        $pos = strpos($string, $search);

        if ($pos === false) {
            break;
        }
    }

    return $string;
}

使用示例:

$search  = 'foo';
$replace = 'bar';
$string  = 'foo wizard makes foo brew for evil foo and jack';
$limit   = 2;

$replaced = str_replace_limit($search, $replace, $string, $limit);

echo $replaced;
// bar wizard makes bar brew for evil foo and jack

我想知道哪一个是最快的，所以我都测试了。

下面你会发现:

这个页面上的所有功能的综合列表 对每个贡献进行基准测试(平均执行时间超过10,000次运行) 链接到每个答案(完整代码)

所有功能都在相同的设置下进行测试:

$string = 'OOO.OOO.OOO.S';
$search = 'OOO'; 
$replace = 'B';

仅替换字符串中字符串第一次出现的函数:

substr_replace($string, $replace, 0, strlen($search)); [CONTRIBUTED BY] => zombat [OOO.OOO.OOO.S] => B.OOO.OOO.S [AVERAGE TIME] => 0.0000062883 [SLOWER BY] => FASTEST replace_first($search, $replace, $string); [CONTRIBUTED BY] => too much php [OOO.OOO.OOO.S] => B.OOO.OOO.S [AVERAGE TIME] => 0.0000073902 [SLOWER BY] => 17.52% preg_replace($search, $replace, $string, 1); [CONTRIBUTED BY] => karim79 [OOO.OOO.OOO.S] => B.OOO.OOO.S [AVERAGE TIME] => 0.0000077519 [SLOWER BY] => 23.27% str_replace_once($search, $replace, $string); [CONTRIBUTED BY] => happyhardik [OOO.OOO.OOO.S] => B.OOO.OOO.S [AVERAGE TIME] => 0.0000082286 [SLOWER BY] => 30.86% str_replace_limit($search, $replace, $string, $count, 1); [CONTRIBUTED BY] => bfrohs - expanded renocor [OOO.OOO.OOO.S] => B.OOO.OOO.S [AVERAGE TIME] => 0.0000083342 [SLOWER BY] => 32.54% str_replace_limit($search, $replace, $string, 1); [CONTRIBUTED BY] => renocor [OOO.OOO.OOO.S] => B.OOO.OOO.S [AVERAGE TIME] => 0.0000093116 [SLOWER BY] => 48.08% str_replace_limit($string, $search, $replace, 1, 0); [CONTRIBUTED BY] => jayoaK [OOO.OOO.OOO.S] => B.OOO.OOO.S [AVERAGE TIME] => 0.0000093862 [SLOWER BY] => 49.26%

仅替换字符串中最后一次出现的字符串的函数:

Substr_replace ($string， $replace, strrpos($string， $search)， strlen($search)); [贡献BY] => oLinkSoftware - modified僵尸 [OOO.OOO.OOO。S] => ooo [平均时间]=> 0.0000068083 [慢]=>最快 Strrev (implode(Strrev ($replace)， explosion (Strrev ($search)， Strrev ($string)， 2))); [贡献BY] => oLinkSoftware [OOO.OOO.OOO。S] => ooo [平均时间]=> 0.0000084460 [慢]=> 24.05%

最简单的方法是使用正则表达式。

另一种方法是用strpos()找到字符串的位置，然后用substr_replace()

但我真的会选择RegExp。