Php regular expression entry (1/5)

Source: Internet
Author: User
Tags php regular expression regular expression

Let's take a look at two special characters: '^' and '$'. They are used to match the start and end of the string respectively. The following are examples:

"^ The": matches strings starting with ";

"Of despair $": match the string ending with "of despair;

"^ Abc $": matches strings starting with abc and ending with abc. In fact, only abc matches;

"Notice": matches a string containing notice;

You can see that if you do not use the two characters we mentioned (the last example), that is, the pattern (regular expression) can appear anywhere in the string to be tested, you didn't lock him to either side.

How many characters are there: '*', '+', and '? ', Which indicates the number or sequence of occurrences of a character. they indicate: "zero or more", "one or more", and "zero or one. "Here are some examples:

"AB *": matches strings a and 0 or more B ("a", "AB", "abbb", etc .);

"AB +": same as above, but at least one B ("AB", "abbb", etc .);

"AB? ": Matches 0 or 1 B;

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