Get count of substring occurrence in an array

Question

I would like to get a count of how many times a substring occurs in an array. This is for a Drupal site so I need to use PHP code

$ar_holding = array('usa-ny-nyc','usa-fl-ftl', 'usa-nj-hb', 
                    'usa-ny-wch', 'usa-ny-li');

I need to be able to call a function like foo($ar_holding, 'usa-ny-'); and have it return 3 from the $ar_holding array. I know about the in_array() function but that returns the index of the first occurrence of a string. I need the function to search for substrings and return a count.

Ilmari Karonen · Accepted Answer · 2011-10-03 17:59:34Z

6

You could use preg_grep():

$count = count( preg_grep( "/^usa-ny-/", $ar_holding ) );

This will count the number of values that begin with "usa-ny-". If you want to include values that contain the string at any position, remove the caret (^).

If you want a function that can be used to search for arbitrary strings, you should also use preg_quote():

function foo ( $array, $string ) {
    $string = preg_quote( $string, "/" );
    return count( preg_grep( "/^$string/", $array ) );
}

answered Oct 3, 2011 at 17:59

Ilmari Karonen

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hakre · Accepted Answer · 2011-10-03 17:48:41Z

3

If you need to search from the beginning of the string, the following works:

$ar_holding = array('usa-ny-nyc','usa-fl-ftl', 'usa-nj-hb', 
                    'usa-ny-wch', 'usa-ny-li');

$str = '|'.implode('|', $ar_holding);

echo substr_count($str, '|usa-ny-');

It makes use of the implode function to concat all array values with the | character in between (and before the first element), so you can search for this prefix with your search term. substr_count does the dirty work then.

The | acts as a control character, so it can not be part of the values in the array (which is not the case), just saying in case your data changes.

answered Oct 3, 2011 at 17:48

hakre

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Niet the Dark Absol · Accepted Answer · 2011-10-03 17:48:08Z

1

$count = subtr_count(implode("\x00",$ar_holding),"usa-ny-");

The \x00 is to be almost-certain that you won't end up causing overlaps that match by joining the array together (the only time it can happen is if you're searching for null bytes)

answered Oct 3, 2011 at 17:48

Niet the Dark Absol

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1 Comment

Ilmari Karonen Over a year ago

This might return a larger count than expected if the array includes values like "usa-ny-foobar-usa-ny-whatever". Admittedly, that seems unlikely in this example, but it's worth noting. (If you only want anchored matches, hakre's trick of including the delimiter in the search string works, though.)

mickmackusa · Accepted Answer · 2018-04-01 12:31:33Z

0

I don't see any reason to overcomplicate this task.

Iterate the array and add 1 to the count everytime a value starts with the search string.

Code: (Demo: https://3v4l.org/5Lq3Y )

function foo($ar_holding, $starts_with) {
    $count = 0;
    foreach  ($ar_holding as $v) {
        if (strpos($v, $starts_with)===0) {
            ++$count;
        }
    }
    return $count;
}

$ar_holding = array('usa-ny-nyc','usa-fl-ftl', 'usa-nj-hb', 
                    'usa-ny-wch', 'usa-ny-li');
echo foo($ar_holding, "usa-ny-");  // 3

Or if you don't wish to declare any temporary variables:

function foo($ar_holding, $starts_with) {
    return sizeof(
        array_filter($ar_holding, function($v)use($starts_with){
             return strpos($v, $starts_with)===0;
        })
    );
}

edited Apr 1, 2018 at 12:31

answered Apr 1, 2018 at 12:24

mickmackusa♦

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