Unset array if preg_match does not match pattern?

Question

I have a multidimensional array that looks like this:

Array
(
    [0] => Array
        (
            [0] => Title 1
            [1] => Some text ... US5801351017 ...
        )

    [1] => Array
        (
            [0] => Title 2
            [1] => Some text ... US0378331005 ...
        )

    [2] => Array
        (
            [0] => Title 3
            [1] => Some text ... //Note here that it does not contain an ISIN Code
        )
...

I am trying to filter out the arrays that match my Regex containg an ISIN Code. The array above was produced from the following code:

$title = $html->find("h3.r a");
$titlearray = array_map(function($value){
    return trim($value->plaintext);
}, $title);

$description = $html->find("span.st");
$descriptionarray = array_map(function($value){
    $string = strip_tags($value);
    return $string;
}, $description);

$result1 = array();
foreach($titlearray as $key => $value) {
    $tmp = array($value);
    if (isset($descriptionarray[$key])) {
        $tmp[] = $descriptionarray[$key];
    }
    $result1[] = $tmp;
}

print_r($result1);

I have written some code that comes very close but does not really unset the arrays that do not contain an ISIN Code. The code I have is this:

$title = $html->find("h3.r a");
$titlearray = array_map(function($value){
    return trim($value->plaintext);
}, $title);

$description = $html->find("span.st");
$descriptionarray = array_map(function($value){
    $match = array();
    $string = strip_tags($value);
    $pattern = "/[BE|BM|FR|BG|VE|DK|HR|DE|JP|HU|HK|JO|US|BR|XS|FI|GR|IS|RU|LB|"
            . "PT|NO|TW|UA|TR|LK|LV|LU|TH|NL|PK|PH|RO|EG|PL|AA|CH|CN|CL|EE|CA|"
            . "IR|IT|ZA|CZ|CY|AR|AU|AT|IN|CS|CR|IE|ID|ES|PE|TN|PA|SG|IL|US|MX|"
            . "SK|KRSI|KW|MY|MO|SE|GB|GG|KY|JE|VG|NG|SA|MU]{2}[A-Z0-9]{10}/";
    preg_match($pattern, $string, $match);
    return $match;
}, $description);

$merged = array();
$i=0;
foreach($descriptionarray as $value){
  $merged[$i] = $value;
  $merged[$i][] = $titlearray[$i];
  $i++;
}

print_r($merged);

which gives me these arrays:

Array
(
    [0] => Array
        (
            [0] => US5801351017
            [1] => Title 1
        )

    [1] => Array
        (
            [0] => US0378331005
            [1] => Title 2
        )

    [2] => Array
        (
            [0] => Title 3
        )
...

How can I get rid of the arrays that do not match my Regex? What I am looking for is this output:

Array
(
    [0] => Array
        (
            [0] => Title 1
            [1] => US5801351017
        )

    [1] => Array
        (
            [0] => Title 2
            [1] => US0378331005
        )
...

---

EDIT

@CasimiretHippolyte

According to his answer, I have this code now:

$titles = $html->find("h3.r a");

$descriptions = $html->find("span.st");

$ISIN_PATTERN = "/[BE|BM|FR|BG|VE|DK|HR|DE|JP|HU|HK|JO|US|BR|XS|FI|GR|IS|RU|LB|"
            . "PT|NO|TW|UA|TR|LK|LV|LU|TH|NL|PK|PH|RO|EG|PL|AA|CH|CN|CL|EE|CA|"
            . "IR|IT|ZA|CZ|CY|AR|AU|AT|IN|CS|CR|IE|ID|ES|PE|TN|PA|SG|IL|US|MX|"
            . "SK|KRSI|KW|MY|MO|SE|GB|GG|KY|JE|VG|NG|SA|MU]{2}[A-Z0-9]{10}/";

$results = [];

foreach ($descriptions as $k => $v) {
    if (preg_match($ISIN_PATTERN, strip_tags($v), $m)) {
        $results[] = ['Title' => trim($titles[$k]->plaintext), 'ISIN' => $m[1]];
    }
}

print_r($results);

This narrows my array down selecting merely the elements that match the Regex, but it does not display the matches under 'ISIN' => $m[1] . It outputs this:

Array
(
    [0] => Array
        (
            [Title] => Title 1
            [ISIN] => 
        )

    [1] => Array
        (
            [Title] => Title 2
            [ISIN] => 
        )
...

---

FURTHER EDIT

This code solves the issue:

$titles = $html->find("h3.r a");

$descriptions = $html->find("span.st");

$ISIN_PATTERN = "/[BE|BM|FR|BG|VE|DK|HR|DE|JP|HU|HK|JO|US|BR|XS|FI|GR|IS|RU|LB|"
            . "PT|NO|TW|UA|TR|LK|LV|LU|TH|NL|PK|PH|RO|EG|PL|AA|CH|CN|CL|EE|CA|"
            . "IR|IT|ZA|CZ|CY|AR|AU|AT|IN|CS|CR|IE|ID|ES|PE|TN|PA|SG|IL|US|MX|"
            . "SK|KRSI|KW|MY|MO|SE|GB|GG|KY|JE|VG|NG|SA|MU]{2}[A-Z0-9]{10}/";

$results1 = [];

foreach ($descriptions as $k => $v) {
    if (preg_match($ISIN_PATTERN, strip_tags($v), $m)) {
        $results1[] = ['Title' => trim($titles[$k]->plaintext), 'ISIN' => $m[1]];
    }
}

$titlesarray = array_column($results1, 'Title');

$results2 = array_map(function($value){
    $match = array();
    $string = strip_tags($value);
    $pattern = "/[BE|BM|FR|BG|VE|DK|HR|DE|JP|HU|HK|JO|US|BR|XS|FI|GR|IS|RU|LB|"
            . "PT|NO|TW|UA|TR|LK|LV|LU|TH|NL|PK|PH|RO|EG|PL|AA|CH|CN|CL|EE|CA|"
            . "IR|IT|ZA|CZ|CY|AR|AU|AT|IN|CS|CR|IE|ID|ES|PE|TN|PA|SG|IL|US|MX|"
            . "SK|KRSI|KW|MY|MO|SE|GB|GG|KY|JE|VG|NG|SA|MU]{2}[A-Z0-9]{10}/";
    preg_match($pattern, $string, $match);
    return $match;
}, $descriptions);

$descriptionarray = array_column($results2, 0);

$result3 = array();
foreach($titlesarray as $key => $value) {
    $tmp = array($value);
    if (isset($descriptionarray[$key])) {
        $tmp[] = $descriptionarray[$key];
    }
    $result3[] = $tmp;
}

print_r($result3);

I scraped something together very fast as I needed a quick solution. This is highly inefficient given that I use an extra arrar_map(), simplify the arrays into a Simple Array and then join them back together. Apart from that, I repeat my Regex.

---

LAST EDIT

@CasimiretHippolyte answer is the most efficient solution and gives the answer for using either his pattern with $m[1] or my pattern with $m[0].

Answer 1

You can design your code in an other way with a simple foreach and build the result items one by one only when the ISIN code is found:

$titles = $html->find("h3.r a");
$descriptions = $html->find("span.st");

define ('ISIN_PATTERN', '~
 \b  # there is probably a word boundary at the begin of the ISIN code
 (?=([A-Z]{2}[A-Z0-9]{10})\b) # check the format before testing the whole alternation
                              # at the same time, the ISIN is captured in group 1
 (?: # so, this alternation is only here to make the pattern fail or succeed
     C[AHLNRSYZ]|I[DELNRST]|P[AEHKLT]|S[AEIGK]|A[ARTU]|B[EGMR]|L[BKUV]|M[OUXY]|T[HNRW]
     |E[EGS]|G[BGR]|H[KRU]|J[EOP]|K[RWY]|N[GLO]|D[EK]|F[IR]|R[OU]|U[AS]|V[EG]|XS|ZA
 )~x');

$results = [];

foreach ($descriptions as $k => $v) {
    if (preg_match(ISIN_PATTERN, strip_tags($v), $m))
        $results[] = [ 'ISIN' => $m[1], 'Title' => trim($titles[$k]->plaintext) ]; 
}

print_r($results);

Note: this code is not tested and can probably be improved. Several ideas:

• stop to use simplehtml and use DOMDocument and DOMXPath
• the hand driven pattern is designed with the assumption that all countries are equiprobable. If it isn't the case, rewrite it to check the most current countries in priority