Okay so first of all, converting one set of characters [eg: accented] to an equivalent form [eg: unaccented] according to some rules is called "transliteration".
The intl extension provides a handy transliterator class that we can invoke with simply:
$translit = Transliterator::create('Latin-ASCII;');
$foo = $translit->transliterate('Français'); // Francais
So painstakingly maintaining a list of "unwanted" characters and their replacements is not necessary.
Secondly, accented characters are not always single codepoints, ç may be represented by either the unified codepoint, or a two-codepoint sequence consisting of a plain c and a combining mark representing the accent.
The unit comprising a single visual glyph is referred to as a Grapheme.
Thirdly, the your requirements [case-insensitve and accent-insensitive] essentially requires that we have to build our own custom string matching procedure.
First, we need a GraphemeIterator to traverse the UTF8 string properly. intl's IntlBreakIterator::createCharacterInstance() does the heavy lifting, but returns byte offsets, so lets wrap that in another iterator that actually pops out graphemes:
class GraphemeIterator implements \Iterator {
protected $i, $string, $offset;
public function __construct($string) {
$this->string = $string;
$i = IntlBreakIterator::createCharacterInstance();
$i->setText($string);
$this->i = $i->getIterator();
$this->init();
}
protected function init() {
$this->offset = $this->i->current();
$this->i->next();
}
public function length() {
return grapheme_strlen($this->string);
}
public function tell() {
return [ $this->offset, $this->i->current()];
}
// Iterator Interface functions
public function current(): mixed {
return substr($this->string, $this->offset, $this->i->current() - $this->offset);
}
public function key(): mixed {
return $this->i->key();
}
public function next(): void {
$this->offset = $this->i->current();
$this->i->next();
}
public function rewind(): void {
$this->i->rewind();
$this->init();
}
public function valid(): bool {
return $this->i->valid();
}
}
Now we need something that can compare two strings after applying some arbitrary comparisons:
class TransformingComparator {
protected $transforms = [];
public function __construct(array $transforms) {
foreach($transforms as $transform) {
$this->addTransform($transform);
}
}
protected function addTransform(callable $transform) {
$this->transforms[] = $transform;
}
protected function transform($input) {
$output = $input;
foreach($this->transforms as $transform) {
$output = $transform($output);
}
return $output;
}
public function compare($a, $b) {
return $this->transform($a) <=> $this->transform($b);
}
}
and a function that can use those to locate the occurrences of the search string:
function findAllInGraphemeString($needle, $haystack, $comparator) {
$t_it = new GraphemeIterator($haystack);
$s_it = new GraphemeIterator($needle);
$s = 0;
$sl = $s_it->length();
$out = [];
$cur = [];
for( $t=0, $tl=$t_it->length(); $t<$tl; ++$t ) {
if( $comparator($t_it->current(), $s_it->current()) === 0 ) {
if( empty($cur) ) {
$cur[] = $t_it->tell()[0];
}
if( ++$s >= $sl ) {
$cur[] = $t_it->tell()[1];
$out[] = $cur;
$cur = [];
$s = 0;
$s_it->rewind();
} else {
$s_it->next();
}
$t_it->next();
} else {
// on aborted partial match restart from current
if( count($cur) != 0 ) {
$s = 0;
$cur=[];
--$t;
} else {
$t_it->next();
}
$s_it->rewind();
}
}
return $out;
}
and finally a function that can perform the actual transformation:
function transformSubstrings(string $text, array $boundaries, callable $transform) {
$output = '';
$offset = 0;
foreach($boundaries as $bound) {
$output .= substr($text, $offset, $bound[0]-$offset);
$output .= $transform(substr($text, $bound[0], $bound[1]-$bound[0]));
$offset = $bound[1];
}
return $output . substr($text, $bound[1]);
}
We can finally put this together as::
$translit = Transliterator::create('Latin-ASCII;');
$transforms = [
[$translit, 'transliterate'], // remove accents
'mb_strtolower'
];
$tc = new TransformingComparator($transforms);
$text = 'lorem ipsum frFrançais dolor sit français amet adsplicing dit';
$search = 'Francais';
echo transformSubstrings(
$text,
findAllInGraphemeString($search, $text, [$tc, 'compare']),
function($a){
return sprintf('<mark>%s</mark>', $a);
}
);
Output:
lorem ipsum <mark>Français</mark> dolor sit <mark>français</mark> amet adsplicing dit <mark>francais</mark>
and yes, I got nerd sniped hard on this one.
Edit: Now that you've mentioned collations it occurs to me that intl has a Collator class, and it looks like TransformingComparator is now longer relevant and can be substituted out like:
$col = new Collator('fr-ca'); // or whatever locale you're using
$col->setStrength(Collator::PRIMARY);
// ...
transformSubstrings(
$text,
findAllInGraphemeString($search, $text, [$col, 'compare']),
function($a){
return sprintf('<mark>%s</mark>', $a);
}
)
Which will likely also be a fair bit faster, since it's likely using a lookup instead of running all the transforms.
