CODEWITHSUNDEEP
phpregex
Anocc Linn
Anocc Linn

Reputation: 85

Get string with number of specified length

Supposing there's an array as the following:

$arr = array('foo1234bar', 'foo1234', '1234bar', 'foo12345bar');

and I just need the elements that contains 4 characters in total only. So except for foo12345bar, other 3 elements are valid.

Because '\d{4}' would match foo12345bar, so I try following clumsily:

$arr = array('foo1234bar', 'foo1234', '1234bar', 'foo12345bar');
$result = array();
foreach ($arr as $value) {
    preg_match('/\d+/', $value, $match);
    if (strlen($match[0]) != 4) {
        continue;
    }
    $result[] = $value;
}
var_dump($result);    //array('foo1234bar', 'foo1234', '1234bar')

Is there a regular expression to match directly(so the if condition can be omitted)? Thank you in advance.

Upvotes: 2

Views: 86

Answers (6)

fusion3k
fusion3k

Reputation: 11689

This regular expression will work on all your examples:

'/^\D*(\d{4})\D*$/'
  ││   │     │  └── end string
  ││   │     └───── zero or more NOT digits
  ││   └─────────── four digits ( match 1 )
  │└─────────────── zero or more NOT digits
  └──────────────── start string

They doesn't work if there are multiple number group in the string ( '123abc1234o' ).

Upvotes: 0

DonCallisto
DonCallisto

Reputation: 29912

Modify your regex as follows

/^\D*\d{4}\D*$/

Explaination

^ your string must start with
\D any non-digit char
* repeated from 0 to infinite times
\d{4} followed by any digit repeated EXACTLY 4 times
\D followed by any non-digit char
* repeated from 0 to infinite times
$ end of the string

Moreover you could modify your code as follows

$arr = array('foo1234bar', 'foo1234', '1234bar', 'foo12345bar');
$result = array_filter(
    $arr,
    function($element) {
        return preg_match('/^\D*\d{4}\D*$/', $element); 
    }
);

var_dump($result);

 Pay attention

As OP didn't specify it, this regex will match even 1234 (any four digit string without non-digit chars in front or behind). If he wishes to have at least a char in front or/and behind, this regex must be changed.

Upvotes: 1

anubhava
anubhava

Reputation: 785146

This easy to handle with look-around regex and preg_grep function:

$arr = array('foo1234bar', 'foo1234', '1234bar', 'foo12345bar');
print_r(preg_grep('/(?<!\d)\d{4}(?!\d)/', $arr));

RegEx Breakup:

(?<!\d)  # assert previous char is not a digit
\d{4}    # match exact 4 digits
(?!\d)   # assert next char is not a digit

Output:

Array
(
    [0] => foo1234bar
    [1] => foo1234
    [2] => 1234bar
)

Upvotes: 5

Aaron Christiansen
Aaron Christiansen

Reputation: 11807

Assuming the characters in front of and after the numbers will always be alphabetical, you can use this regex:

^[a-zA-Z]*\d{4}[a-zA-Z]+$

Upvotes: 1

l3lackwolf
l3lackwolf

Reputation: 96

you might try folowing :
preg_match('/\D\d{4}\D/', $value, $match);

it searches for:

a not digit(/D)
4 digits(/d{4})
again a non digit(/D)

Upvotes: 0

&#193;lvaro Touz&#243;n
&#193;lvaro Touz&#243;n

Reputation: 1230

the regexp will be \d{4}

 preg_match('/\d{4}/', $value, $match);

expect will help

Upvotes: 0

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