Escape REGEXP for MariaDB query

mariadb-escape-regexp.php

<?php

// MariaDB uses the C escape syntax in strings (for example, "\n" to represent the newline character), 
// we must double any "\" that we use in REGEXP strings (see https://mariadb.com/kb/en/regexp/)
// PHP's preg_quote() won't work here as it adds single slashes so use a special regular expression here
$string = 'My [string] {with} ~regexp~ |special| /characters/+.';
$pattern = '/(\+|-|\||&&|\|\||!|\(|\)|\{|}|\[|]|\^|"|~|\*|\?|:|\\\)/';
$replacement = '\\\\\\\\${1}';
$stringEscaped = preg_replace($pattern, $replacement, $string);

// use string in MariaDB REGEXP functions
$query = <<<SQL
    SELECT * FROM my_table
    WHERE my_column REGEXP '{$stringEscaped}'
SQL;