php preg_filter performs a regular expression search and replace

php preg_filter performs a regular expression search and replace_PHP tutorial

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Release： 2016-07-21 15:20:32

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preg_filter
(PHP 5 >= 5.3.0)

preg_filter — Perform a regular expression search and replace
mixed preg_filter ( mixed $pattern , mixed $replacement , mixed $subject [, int $limit = -1 [, int &$count ]] )
preg_filter() is equivalent to preg_replace() except that it only returns (possibly transformed) results that match the target. For more details on how this function works please Read the preg_replace() documentation.

Return Value
If subject is an array, returns an array, otherwise returns a string.

If no match is found or an error occurs, when When subject is an array, an empty array is returned, otherwise NULL is returned.

Example

Example #1 Example of comparing preg_filter() and preg_replace()

Copy code The code is as follows:

 
$subject = array('1', 'a', '2', 'b', '3', 'A', 'B', '4'); 
$pattern = array('/d/', '/[a-z]/', '/[1a]/'); 
$replace = array('A:$0', 'B:$0', 'C:$0'); 

echo "preg_filter returnsn"; 
print_r(preg_filter($pattern, $replace, $subject)); 

echo "preg_replace returnsn"; 
print_r(preg_replace($pattern, $replace, $subject)); 
?> 

The above routine will output:

Copy code The code is as follows:

 
preg_filter returns 
Array 
( 
[0] => A:C:1 
[1] => B:C:a 
[2] => A:2 
[3] => B:b 
[4] => A:3 
[7] => A:4 
) 
preg_replace returns 
Array 
( 
[0] => A:C:1 
[1] => B:C:a 
[2] => A:2 
[3] => B:b 
[4] = > A:3 
[5] => A 
[6] => B 
[7] => A:4 
) 

PCRE Patterns
preg_replace() - performs a regular expression search and replace
preg_replace_callback() - performs a regular expression search and replaces with a callback
preg_grep() - Returns array entries matching a pattern
preg_last_error() - Returns the error code generated by the last PCRE regular execution