PHP regular expression, match the last occurence

user_2217647 0
Viewed 106

I have a php function that splits product names from their color name in woocommerce. The full string is generally of this form "product name - product color", like for example:

"Boxer Welbar - ligth grey" splits into "Boxer Welbar" and "light grey"

"Longjohn Gari - marine stripe" splits into "Longjohn Gari" and "marine stripe"

But in some cases it can be "Tee-shirt - product color"...and in this case the split doesn't work as I want, because the "-" in Tee-shirt is detected.

How to circumvent this problem? Should I use a "lookahead" statement in the regexp?

function product_name_split($prod_name) {
    $currenttitle = strip_tags($prod_name);

    $splitted = preg_split("/–|[\p{Pd}\xAD]|(–)/", $currenttitle);

    return $splitted;
}
woocommerce php regex
5 Answers

I'd go for a negative lookahead.

Something like this:

-(?!.*-)

that means to search for a - not followed by any other -

This works if in the color name there will never be a -

user_23990350

What about counting space characters that surround a dash?

For example:


function product_name_split($prod_name) {
  $currenttitle = strip_tags($prod_name);

  $splitted = preg_split("/\s(–|[\p{Pd}\xAD]|(–))\s/", $currenttitle);

  return $splitted;
}

This automatically trims spaces from split parts as well.

user_6179500

If you have - as delimiter (note the spaces around the dash), you may simply use explode(...). If not, use

\s*-(?=[^-]+$)\s*

or

\w+-\w+(*SKIP)(*FAIL)|-

with preg_split(), see the demos on regex101.com (#2)

In PHP this could be:

<?php
$strings = ["Tee-shirt - product color", "Boxer Welbar - ligth grey", "Longjohn Gari - marine stripe"];

foreach ($strings as $string) {
    print_r(explode(" - ", $string));
}

foreach ($strings as $string) {
    print_r(preg_split("~\s*-(?=[^-]+$)\s*~", $string));
}
?>

Both approaches will yield

Array
(
    [0] => Tee-shirt
    [1] => product color
)
Array
(
    [0] => Boxer Welbar
    [1] => ligth grey
)
Array
(
    [0] => Longjohn Gari
    [1] => marine stripe
)

To collect the splitted items, use array_map(...):

$splitted = array_map( function($item) {return preg_split("~\s*-(?=[^-]+$)\s*~", $item); }, $strings);
user_12314500

Your sample inputs convey that the neighboring whitespace around the delimiting hyphen/dash is just as critical as the hyphen/dash itself.

I recommend doing all of the html and special entity decoding before executing your regex -- that's what these other functions are built for and it will make your regex pattern much simpler to read and maintain.

\p{Pd} will match any hyphen/dash. Reinforce the business logic in the code by declaring a maximum of 2 elements to be generated by the split.

As a general rule, I discourage declaring single-use variables.

Code: (Demo)

function product_name_split($prod_name) {
    return preg_split(
        "/ \p{Pd} /u",
        strip_tags(
            html_entity_decode(
                $prod_name
            )
        ),
        2
    );
}

$tests = [
    'Tee-shirt - product color',
    'Boxer Welbar - ligth grey',
    'Longjohn Gari - marine stripe',
    'En dash – green',
    'Entity &#8211; blue',
];

foreach ($tests as $test) {
    echo var_export(product_name_split($test, true)) . "\n";
}

Output:

array (
  0 => 'Tee-shirt',
  1 => 'product color',
)
array (
  0 => 'Boxer Welbar',
  1 => 'ligth grey',
)
array (
  0 => 'Longjohn Gari',
  1 => 'marine stripe',
)
array (
  0 => 'En dash',
  1 => 'green',
)
array (
  0 => 'Entity',
  1 => 'blue',
)
user_29434030

As usual, there are several options for this, this is one of them

  • explode — Split a string by a string

  • end — Set the internal pointer of an array to its last element

$currenttitle = 'Tee-shirt - product color';

$array = explode( '-', $currenttitle );

echo end( $array );
user_119875380
Related