preg_match()

The preg_match() function in PHP is used for performing regular expression matches. It is part of PHP's PCRE (Perl Compatible Regular Expressions) functions, which are a set of functions that implement regular expression pattern matching using a syntax that is mostly compatible with Perl's regular expressions.

The syntax is:

int preg_match ( string $pattern , string $subject [, array &$matches [, int $flags = 0 [, int $offset = 0 ]]] )
  • Parameters:
    • $pattern: The regular expression pattern.
    • $subject: The input string.
    • $matches (optional): An array that is filled with the search results.
    • $flags (optional): Flags to control the match.
    • $offset (optional): An alternative starting point within $subject.
  • Return Value: preg_match returns 1 if the pattern matches, 0 if it does not, or FALSE if an error occurs.

An example may be:

if (preg_match("/^example$/", "example")) {
    // The pattern matches the string "example"
}

Regular expressions, and by extension preg_match(), are often used in input validation. Proper input validation is a key aspect of securing applications against various forms of injection attacks, including SQL injection (SQLi).

However, preg_match() by itself does not prevent SQLi. It can be part of a broader strategy for ensuring that inputs conform to expected formats (like checking if an input is a valid email address, phone number, etc.), which indirectly reduces the risk of injection attacks.