[Regular expression] asks a regular expression segmentation question. online solution ~ Objective: to use a regular expression to separate keywords. Assume that the keyword is (with multiple spaces in the middle): You & nbsp; I & nbsp; she uses the asterisk: print_r (preg_split (s *), & nbsp; $ _ POST [query]); result: Array & nbsp; (& nbsp; [0] & nbsp; & gt; & [regular expression] ask a question about regular expression Segmentation. online solution ~
Objective: to use a regular expression to separate keywords.
Assume that the keyword is (with multiple spaces in the middle): You and her
Use asterisks:
print_r(preg_split("/(\s*)/", $_POST['query']));
Result: Array ([0] => [1] =>? [2] =>? [3] =>? [4] => [5] =>? [6] =>? [7] =>? [8] => [9] =>? [10] =>? [11] =>? [12] =>)
Use the plus sign: print_r (preg_split ("/(\ s +)/", $ _ POST ['query']);
Result: Array ([0] => you [1] => I [2] => She)
Why?
Regular expression manual:
* Matches the previous subexpression zero or multiple times. For example, zo * can match "z" and "zoo ". * Is equivalent to {0 ,}.
+ Match the previous subexpression once or multiple times. For example, 'Zo + 'can match "zo" and "zoo", but cannot match "z ". + Is equivalent to {1 ,}.
Is one matching zero or multiple times, and one matching once or multiple times, that the difference is so big? Why can't I understand why asterisks cause garbled characters ~~~
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* It can be 0 times. do you need to distinguish by space? There are also numbers of spaces ~
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It should have matched 0 times.
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\ S * May match 0 characters between the first and second bytes of your encoding, so garbled characters are generated.
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Why use split? is it difficult to directly match a non-empty string?
