PHP Regex; extract first matching ID in WordPress shortcode

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Having this string 

$string = '';

How could I extract the first id in ids?

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So far I have succeeded to extract all the ids, then used split; 

$output = preg_match_all('/(.+?)['"]]/', $string, $matches);
list($extracted) = split(',', $matches[1][0]);

There must be something simpler using only regex, right?

Thanks 🙂

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3 comments

  1. You could try the below regex to match the first id in id’s,

    [gallery.+ids="K[^,]*

    OR

    [gallery.+ids="Kd+

    DEMO

    Your PHP code would be,

    <?php
$string = '[gallery link="file" ids="501,502,503,504,505,506,507,508,509"]';
$pattern = '~[gallery.+ids="K([^,]*)~';
if (preg_match($pattern, $string, $m)) {
    $yourmatch = $m[0]; 
    echo $yourmatch;
    }
?> //=> 501

  2. How could I extract the first id in ids?

    Get the matched group from index 1.

    bids="(d+)

    Here is DEMO

    OR try with Positive Lookbehind

    (?<=bids=")d+

    Here is DEMO

    Sample code:

    $re = "/(?<=\bids=")\d+/";
$str = "[gallery link="file" ids="501,502,503,504,505,506,507,508,509"]";

preg_match_all($re, $str, $matches);

  3. Whatever you are trying here looks weird. You don’t need regular expressions to get the shortcode params. Instead use the default, built-in function from WordPress.

    Example from codex.wordpress.org:

    // [bartag foo="foo-value"]
function bartag_func( $atts ) {
    $a = shortcode_atts( array(
        'foo' => 'something',
        'bar' => 'something else',
    ), $atts );

    return "foo = {$a['foo']}";
}
add_shortcode( 'bartag', 'bartag_func' );

    See: WordPress Codex – The Shortcode API

    Update – get the first ID:

    // [gallery link="file" ids="501,502,503,504,505,506,507,508,509"]
function gallery_shortcode( $atts ) {
    $atts = shortcode_atts( array(
        'link' => 'file',
        'ids' => array(),
    ), $atts );

    $ids = explode( ',', $atts );

    // strip the first ID from the array…
    $first_id = array_shift( $ids );
    // …or just select it
    $first_id = $ids[0];

    return $first_id;
}
add_shortcode( 'gallery', 'gallery_shortcode' );