替换单个字符或多个字符

Question

I want to replace newline \n . If there is one occurrence it gets replaced with <br> . If there are two or more in a row it gets replaced with <br><br> . I can do either or but I am not sure how to do both for the same variable.

Answer 1

If you want to replace two or more with the same number of line breaks, str_replace should work.

str_replace("\n", '<br />', $text);

If however, you want to replace three newline characters with only two line breaks then you'll have to perform two replaces, at least one using a regular expression:

$text = preg_replace('/\n{2,}/', "<br /><br />", $text);
$text = str_replace("\n", '<br />', $text);

Answer 2

How about:

$pattern = array("/\n\n+/", "/\n/");
$replacement = array('<br/><br/>',  '<br/>' );
$str = "The quick \nbrown fox \n\n\njumps over \n\nthe lazy dog.";

$result = preg_replace($pattern, $replacement, $str);

Just replace <br/> with <br> if <br> is what you really want.

Answer 3

As a (hopefully simpler) variant of Godwin's solution, try:

$text = str_replace("\n\n", '<br /><br />', $text);
$text = str_replace("\n", '<br />', $text);

This will replace any 2 successive newlines with 2 line breaks, then if there are any single newlines remaining, they will be replaced by single line breaks. This would implement your substitutions for 1, 2, or 3 (or more) successive newlines.