PHP - UNSET values in array not containing prefix

Question

I have an array like:

$array  = array('OPTM3000', 'All-Stud','OPTM3002','MUSC1001','PATH3000', 'OPTM3004');

I want to UNSET the values in the array that are not prefixed with OPTM.

How should that be done?

PHP 5.5

unset or remove? Do you want to preserve in index positions (e.g. OPTM3002 stays at index 2 or does it become 1)? — Salman A, Sep 30 '21 at 08:39
Does this answer your question? [Unset array Items matching a pattern](https://stackoverflow.com/questions/9444427/unset-array-items-matching-a-pattern) — thchp, Sep 30 '21 at 08:40

score 1 · Answer 1 · answered Sep 30 '21 at 08:41

// Don't need this if using PHP 8
if (!function_exists('str_starts_with')) {
    function str_starts_with($haystack, $needle) {
        return (string)$needle !== '' && strncmp($haystack, $needle, strlen($needle)) === 0;
    }
}

$array = array('OPTM3000', 'All-Stud','OPTM3002','MUSC1001','PATH3000', 'OPTM3004');
for ($i = 0; $i < count($array); ++$i) {
    if (!str_starts_with($array[$i], 'OPTM'))
        unset($array[$i]);
}

// Optional to re-index array
$array = array_values($array);

score 1 · Answer 2 · answered Sep 30 '21 at 08:41

1

You can use foreach/str_contains/unset like:

$array  = array('OPTM3000', 'All-Stud','OPTM3002','MUSC1001','PATH3000', 'OPTM3004');
foreach($array as $key => $value){
    if(!str_contains($value,'OPTM')){
        unset($array[$key]);
    }
}
print_r($array); 
/*
Array
(
    [0] => OPTM3000
    [2] => OPTM3002
    [5] => OPTM3004
)

*/

Reference:

answered Sep 30 '21 at 08:41

Simone Rossaini

8,115
1
13
34

1

PS str_contains is php8+, but this will check if the prefix is *anywhere in the string*, but OP want to check if it's a *prefix*, which means you'll have to use str_starts_with – hanshenrik Sep 30 '21 at 08:48

score 1 · Answer 3 · answered Sep 30 '21 at 08:46

1

Use this

$array  = array('OPTM3000', 'All-Stud','OPTM3002','MUSC1001','PATH3000', 'OPTM3004');

$new_array = array_filter($array, function($v,$k) {
    return strpos($v,'OPTM') !==false;
}, ARRAY_FILTER_USE_BOTH);

answered Sep 30 '21 at 08:46

Feyzili Mikayıl

9
1

This unexplained answer will match any string the "contains" the needle, not only if the "starts with" the needle. This question asks to match "prefixes". – mickmackusa Nov 30 '22 at 21:02

score 1 · Answer 4 · answered Sep 30 '21 at 08:49

1

try this

$array  = array('OPTM3000', 'All-Stud','OPTM3002','MUSC1001','PATH3000', 'OPTM3004');

$newArray = array();

foreach($array as $value) {
  if ( 'OPTM' == substr($value, 0, 4) ) {
     $newArray[] = $value;
  }
}

answered Sep 30 '21 at 08:49

Bhanu Pratap

144
6

score 1 · Answer 5 · answered Sep 30 '21 at 08:52

1

Use Unset or if you don like to use unset function one possible way will be to work with array_map and array_filter:

$array  = array('OPTM3000', 'All-Stud','OPTM3002','MUSC1001','PATH3000', 'OPTM3004');
$arr = array_map(function($item) {
    if ( str_contains($item,'OPTM')) {
      return $item;    
    }
}, $array);

$arr = array_filter($arr);
print_r($arr);

answered Sep 30 '21 at 08:52

Maik Lowrey

15,957
6
40
79

This unexplained answer will match any string the "contains" the needle, not only if the "starts with" the needle. This question asks to match "prefixes". – mickmackusa Nov 30 '22 at 21:03

Armen Grigoryan · Accepted Answer · 2021-09-30T10:22:29.933

A short approach to reach the same value

$array  = array('OPTM3000', 'All-Stud','OPTM3002','MUSC1001','PATH3000', 'OPTM3004');

$filtred = array_filter($array, function($item){
    return  (strncmp($item, 'OPTM', 4)==0);
});

var_dump($filtred);

to make your code more dynamic and optimal you can do like this

$array  = array('OPTM3000', 'All-Stud','OPTM3002','MUSC1001','PATH3000', 'OPTM3004');

$prefix = 'OPTM';
$array = array_filter($array, function($item) use($prefix){
    return  (strncmp($item, $prefix, strlen($prefix))==0);
});

var_dump($array);

score 0 · Answer 7 · answered Sep 30 '21 at 08:48

0

You can iterate the elements in your array using a regex like:

foreach($array as $element){
    $pattern = "OPTM/";
    if(echo preg_match($pattern, $element) == 0){
        $key = array_search($element, $array);
        unset($array[$key]);
    }
}

answered Sep 30 '21 at 08:48

s_frix

323
2
11

This is not efficient code. The `foreach()` will deliver the key if you declare it. – mickmackusa Nov 30 '22 at 21:01

score 0 · Answer 8 · answered Sep 30 '21 at 08:52

OK, this works for me.

$array  = array('OPTM3000', 'All-Stud','OPTM3002','MUSC1001','PATH3000', 'OPTM3004');
            
$allowed_prefix = 'OPTM';

foreach ( $array as $key => $text )  
{
    if (strpos($text, $allowed_prefix) !== 0) {
        unset($array[$key]);
    }
}

PHP - UNSET values in array not containing prefix

8 Answers8