Can PHP use regular expressions?

Regular expression (regular expression) is a text pattern, including ordinary characters and special characters (metacharacters). Regular expressions use a single string to describe and match a series of strings that match a certain syntax rule.

Through regular expressions, you can:

Test patterns within strings (data validation), replace text, based on patterns Matching extracts substrings from strings (recommended learning: PHP programming from entry to proficiency)

In PHP, preg_math() and preg_match_all functions are provided for regular matching. The prototypes of these two functions are as follows:

int preg_match|preg_match_all ( string $pattern , string $subject [, array &$matches [, int $flags = 0 [, int $offset = 0 ]]] )

Search for a match between subject and the regular expression given by pattern.

pattern: pattern to be searched, string type.

subject: Input string.

matches: If the parameter matches is provided, it will be populated as the search results. matches[0] will contain the text matched by the complete pattern, matches[1] will contain the text matched by the first capturing subgroup, and so on.

flags:

flags can be set to the following flag values: PREG_OFFSET_CAPTURE If this flag is passed, for each occurrence of a match the string offset (relative to the target character) will be returned appended string).

Note: This will change the array filled in the matches parameter so that each element becomes a string with the 0th element being the matched string and the 1st element being the match. The offset of the string in the target string subject.

offset: Usually, the search starts from the beginning of the target string. The optional parameter offset is used to specify the search starting from an unknown point in the target string (unit is bytes).

Return value:

preg_match() returns the number of matches for pattern. Its value will be 0 (no match) or 1 because preg_match() will stop searching after the first match. preg_match_all() is different from this, it will search the subject until it reaches the end. If an error occurs preg_match() returns FALSE.

Use regular rules

Because we only need to determine whether it exists, we choose preg_match.

$str='http://blog.csdn.net/hsd2012';
$pattern='/csdn/';
function checkStr2($str,$str2)
{
    return preg_match($str2,$str)?true:false;
}
echo checkStr2($str,$pattern);

The above is the detailed content of Can PHP use regular expressions?. For more information, please follow other related articles on the PHP Chinese website!