php 使用 preg_replace 仅替换第一个匹配项
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Replace only first match using preg_replace
提问by deadbeef
I have a string with structure similar to: 'aba aaa cba sbd dga gad aaa cbz'. The string can be a bit different each time as it's from an external source.
我有一个结构类似于：的字符串'aba aaa cba sbd dga gad aaa cbz'。字符串每次都可能有点不同，因为它来自外部源。
I would like to replace only first occurrence of 'aaa'but not the others. Is it possible?
我只想替换第一次出现的'aaa'而不是其他的。是否可以？
回答by Paul
The optional fourth parameter of preg_replaceis limit:
preg_replace的可选第四个参数是limit：
preg_replace($search, $replace, $subject, 1);
回答by codaddict
You can use the limitargument of preg_replacefor this and set it to 1so that at most one replacement happens:
您可以为此使用limit参数preg_replace并将其设置为，1以便最多发生一次替换：
$new = preg_replace('/aaa/','replacement',$input,1);
回答by T.Todua
for example, out $content is:
例如，out $content 是：
START
FIRST AAA
SECOND AAA
1) if you use:
1）如果你使用：
$content = preg_replace('/START(.*)AAA/', 'REPLACED_STRING', $content);
it will change everything from the START to the last AAA and Your result will be:
它将改变从 START 到最后一个 AAA 的所有内容，您的结果将是：
REPLACED_STRING
2) if you use:
2）如果你使用：
$content = preg_replace('/START(.*?)AAA/', 'REPLACED_STRING', $content);
Your Result will be like:
您的结果将类似于：
REPLACED_STRING
SECOND AAA
