php preg_match function 3rd parameter

Question

I was reading the online manual of the preg_match function and wrote up a piece of code to test it. Along with it I wrote up another piece of code using preg_grep.

Here is the code:

$subject = array("Robert");
$subject2 = "Robert";
$pattern = "/./";


$result = preg_grep($pattern, $subject);
$result2 = preg_match($pattern, $subject2, $matches);
echo "<pre>";
print_r($result);
print_r($matches);
echo "</pre>";

For the preg_grep I got what I expected, an array element[0] with the value "Robert", that made sense.

For preg_match I got an unexpected result, at least to my understanding of regexp. It was an array element[0] with the value "R".

Why is that?

Mihai Iorga · Accepted Answer · 2013-03-05 14:33:31Z

3

. matches any character except new line. So it would return first character since + isn't present.

answered Mar 5, 2013 at 14:33

Mihai Iorga

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Comments

Wouter J · Accepted Answer · 2013-03-05 14:52:29Z

2

Because /./ means one character, not all. You should use a quantifier:

* means 0 or more characters
+ means 1 or more characters
? means 0 or 1 character

If you suffix quantifiers with ? it means an ungreedy match (which means that it tries to match as less characters as possible, and not as much characters as possible).

A complete result:

Input string: 'Robert'

Regex    Result
=====    ======

/.*/     Robert
/.*?/    null
/.+/     Robert
/.+?/    R
/.?/     R
/.??/    null

edited Mar 5, 2013 at 14:52

answered Mar 5, 2013 at 14:40

Wouter J

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