小编典典

// New line is required to split non-blank lines

preg_replace("/(^[\r\n]*|[\r\n]+)[\s\t]*[\r\n]+/", "\n", $string);

上面的正则表达式说：

/(^[\r\n]*|[\r\n]+)[\s\t]*[\r\n]+/

1st Capturing group (^[\r\n]*|[\r\n]+)

1st Alternative: ^[\r\n]*

^ assert position at start of the string

[\r\n]* match a single character present in the list below

Quantifier: Between zero and unlimited times, as many times as possible, giving back as needed [greedy]

\r matches a carriage return (ASCII 13)

\n matches a fine-feed (newline) character (ASCII 10)

2nd Alternative: [\r\n]+

[\r\n]+ match a single character present in the list below

Quantifier: Between one and unlimited times, as many times as possible, giving back as needed [greedy]

\r matches a carriage return (ASCII 13)

\n matches a fine-feed (newline) character (ASCII 10)

[\s\t]* match a single character present in the list below

Quantifier: Between zero and unlimited times, as many times as possible, giving back as needed [greedy]

\s match any white space character [\r\n\t\f ]

\tTab (ASCII 9)

[\r\n]+ match a single character present in the list below

Quantifier: Between one and unlimited times, as many times as possible, giving back as needed [greedy]

\r matches a carriage return (ASCII 13)

\n matches a fine-feed (newline) character (ASCII 10)

2020-05-29