Question

我如何用一条新路线取代连续的多条新线。可能相互之间有20条新路线。例如

James said hello



 Test
 Test two

最终如下:

James said hello
 Test
 Test two

Answer 1

引证:

$str = "Hello




World


How
Are

You?";
$str = preg_replace("/
+/", "
", $str);
print($str);

Answer 2

改进马克 B 答案:

$fixed_text  = preg_replace("
(s*
)+", "
", $text_to_fix);

这条新线应当与最初的新线相匹配,然后至少是一组白空间,然后是一条新线,用一条新线取代。

Answer 3

$fixed_text = preg_replace("
+", "
", $text_to_fix);

This should do it, assuming that the consecutive newlines are truly consecutive and don t have any whitespace (tabs, spaces, carriage returns, etc...) between them.

Answer 4

$str =  James said hello



 Test
 Test two

 ;
echo preg_replace( {(\
)1+} , $1 ,$str);

Answer 5

In regex:

+ means "one or more of the previous expression"
{2,} means "two or more of the previous expression"

For the requirements in this question, there is no point replacing a single with a single because nothing changes for that substring. In other words, / +/ is simply doing more work than necessary.

采用两个或两个以上层次的验证方法更有意义。

法典:Demo

$string = "James said hello



 Test
 Test two

";
echo json_encode(
    preg_replace("/
{2,}/", "
", $string)
);

产出:

"James said hello
 Test
 Test two
"

In other situations, it may be advantageous to replace newline sequences that may be from different operating systems with R. This metacharacter matches or . Here is a modified pattern which will replace two or more newline sequences with the server s designated newline character sequence:

$string = "James
 said

 hello


 Test
 Test two

";
echo json_encode(
    preg_replace("/R{2,}/", PHP_EOL, $string)
);
// "James
 said
 hello
 Test
 Test two
"
//       ^^^^----treated as one newline character sequence

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