How can the escape sequence for '[' be properly handled in a regular expression in PHP?

The escape sequence for '[' in a regular expression is '\\['. To properly handle this escape sequence in a regular expression in PHP, you need to double escape the backslash, resulting in '\\\\['. This ensures that the '[' character is treated as a literal character and not as part of a character class. 

$pattern = '/\\[/';
$string = 'This is a [test] string';
if (preg_match($pattern, $string)) {
    echo 'Match found!';
} else {
    echo 'No match found.';
}

Keywords

escape sequence regular expression PHP handling '['

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