php preg_replace assign different replacement pattern for each capturing group

I'm trying to perform a mysql fulltext search in boolean mode and I need to prepare the search text before I build the mysql query.

In order to achieve it, I though I could use the PHP function preg_replace and replace each capturing group by one specific pattern.

preg_replace

"hello world"

+

+"hello world"

+

*

+how*

regex pattern

["']+([^"']+)["']+|([^s"']+)


substitution pattern

+"1" +2*


EXAMPLE

For the following input:

"hello world" how are you?


It should return:

+"hello world" +how* +are* +you?*


But instead, it returns something 'wrong':

+"hello world" +* +"" +how* +"" +are* +"" +you?*


I'm aware that the replacement pattern +"1" +2* will never work since I'm not telling anywhere that +"..." should only apply to the first capturing group and +...* to the second one.

+"1" +2*

+"..."

+...*

Test online regex.

PHP code

$query = preg_replace('~["']+([^"']+)["']+|([^s"']+)~', '+"1" +2*', $query);


Is there a way to achieve this in PHP? Thank you in advance.

EDIT / SOLUTION

Thanks to @revo suggestion to use the PHP function preg_replace_callback, I managed to assign a replace pattern to each search pattern with the extended function preg_replace_callback_array. Please note that this function needs PHP >= 7.

preg_replace_callback

preg_replace_callback_array

Here I post the final version of the function I use to perform a FULLTEXT search via MATCH (...) AGAINST (...) IN BOOLEAN MODE. The function is declared within the class dbReader in a Wordpress Plugin. Maybe it can be useful for someone.

FULLTEXT

MATCH (...) AGAINST (...) IN BOOLEAN MODE

class dbReader

// Return maximum 100 ids of products matching $query in
// name or description searching for each word using MATCH AGAINST in BOOLEAN MODE
public function search_products($query) {

function replace_callback($m, $f) {
return sprintf($f, isset($m[1]) ? $m[1] : $m[0]);
}

// Replace simple quotes by double quotes in strings between quotes:
// iPhone '8 GB' => iPhone "8 GB"
// Apple's iPhone 8 '32 GB' => Apple's iPhone 8 "32 GB"
// This is necessary later when the matches are devided in two groups:
// 1. Strings not between double quotes
// 2. Strings between double quotes
$query = preg_replace("~(s*)'+([^']+)'+(s*)~", '$1"$2"$3', $query);

// Do some magic to take numbers with their units as one word
// iPhone 8 64 GB => iPhone 8 "64 GB"
$pattern = array(
'(b[.,0-9]+)s*(gbb)',
'(b[.,0-9]+)s*(mbb)',
'(b[.,0-9]+)s*(mmb)',
'(b[.,0-9]+)s*(mhzb)',
'(b[.,0-9]+)s*(ghzb)'
);
array_walk($pattern, function(&$value) {
// Surround with double quotes only if the user isn't doing manual grouping
$value = '~'.$value.'(?=(?:[^"]*"[^"]*")*[^"]*Z)~i';
});
$query = preg_replace($pattern, '"$1 $2"', $query);

// Prepare query string for a "match against" in "boolean mode"
$patterns = array(
// 1. All strings not sorrounded by double quotes
'~([^s"]+)(?=(?:[^"]*"[^"]*")*[^"]*Z)~' => function($m){
return replace_callback($m, '+%s*');
},

// 2. All strings between double quotes
'~"+([^"]+)"+~' => function($m){
return replace_callback($m, '+"%s"');
}
);

// Replace every single word by a boolean expression: +some* +word*
// Respect quoted strings: +"iPhone 8"
// preg_replace_callback_array needs PHP Version >= 7
$query = preg_replace_callback_array($patterns, $query);

$fulltext_fields = array(
'title' => array(
'importance' => 1.5,
'table' => 'p',
'fields' => array(
'field1',
'field2',
'field3',
'field4'
)
),
'description' => array(
'importance' => 1,
'table' => 'p',
'fields' => array(
'field5',
'field6',
'field7',
'field8'
)
)
);
$select_match = $match_full = $priority_order = "";

$args = array();
foreach ($fulltext_fields as $index => $obj) {
$match = $obj['table'].".".implode(", ".$obj['table'].".", $obj['fields']);
$select_match .= ", MATCH ($match) AGAINST (%s IN BOOLEAN MODE) AS {$index}_score";
$match_full .= ($match_full!=""?", ":"").$match;
$priority_order.= ($priority_order==""?"ORDER BY ":" + ")."({$index}_score * {$obj['importance']})";
array_push($args, $query);
}
$priority_order .= $priority_order!=""?" DESC":"";

// User input $query is passed as %s parameter to db->prepare() in order to avoid SQL injection
array_push($args, $query, $this->model_name, $this->view_name);

return $this->db->get_col(
$this->db->prepare(
"SELECT p.__pk $select_match
FROM ankauf_... AND
MATCH ($match_full) AGAINST (%s IN BOOLEAN MODE)
INNER JOIN ...
WHERE
m.bezeichnung=%s AND
a.bezeichnung=%s
$priority_order
LIMIT 100
;",
$args
)
);
}


preg_replace_callback

db->prepare("... AGAINST (%s IN BOOLEAN MODE) ...")

1 Answer
1

You have to use preg_replace_callback:

preg_replace_callback

$str = '"hello world" how are you?';

echo preg_replace_callback('~("[^"]+")|S+~', function($m) {
return isset($m[1]) ? "+" . $m[1] : "+" . $m[0] . "*";
}, $str);


Output:

+"hello world" +how* +are* +you?*


Live demo

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