php preg_replace replacement example explanation_PHP tutorial

Copy code The code is as follows:

mixed preg_replace ( mixed $pattern , mixed $replacement , mixed $subject [, int $ limit = -1 [, int &$count ]] )

is a function that performs search and replacement of a regular expression. Usually when we use it, it usually ends with one replacement. Today we saw it again The PHP manual found a relatively difficult (in my opinion) example to share with you.

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_replace returnsn

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

The result is as follows:

At first glance, I was stunned
Generally, if the matching pattern and replacement content are both arrays, they should correspond. If there are fewer elements in replacement than in pattern , the extra pattern is replaced with an empty string.
$pattern is like a scanner. If it finds a match, it is replaced with the corresponding $replace
For the above example, the replacement process is as follows:
/ d/Scan 1 in $subject, and if it matches, if the matching content is $0 (that is, 1), replace 1 with A:1
, and then use /[a-z]/ to scan A:1 if it does not match, then it will not be replaced. Continue to use [1a] to scan A:1, the matching content is 1 (that is, $0), replace the 1 in A:1 with C:1
The first item is finally replaced with A:C:1
Simplify the process:

1->A:1->A:C:1
a->B:a->B:C:a
2->A:2
b ->B:b
A (If there is no match, it will not be replaced)
B (Same as above)
4->A:4
To summarize, take every item in $pattern The pattern matches each element in $subject in turn. When matched, it is replaced with the $replace corresponding to $pattern. As in the above example,

may be replaced more than once.

http://www.bkjia.com/PHPjc/825007.htmlwww.bkjia.comtruehttp: //www.bkjia.com/PHPjc/825007.htmlTechArticleCopy code The code is as follows: mixed preg_replace ( mixed $pattern , mixed $replacement , mixed $subject [, int $limit = -1 [, int lt;?php $subject = array('1', 'a', '2', 'b', '3', 'A'...