PHP regular expression, match the last occurence - php

Question

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;
}

Answer 1

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 -

Answer 2

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.

Answer 3

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);

Answer 4

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
);
}
$tests = [
'Tee-shirt - product color',
'Boxer Welbar - ligth grey',
'Longjohn Gari - marine stripe',
'En dash – green',
'Entity – blue',
];
foreach ($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',
)

Answer 5

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 );