is_serialized( string $data, bool $strict = true ): bool

669function is_serialized( $data, $strict = true ) {670	// If it isn't a string, it isn't serialized.671	if ( ! is_string( $data ) ) {672		return false;673	}674	$data = trim( $data );675	if ( 'N;' === $data ) {676		return true;677	}678	if ( strlen( $data ) < 4 ) {679		return false;680	}681	if ( ':' !== $data[1] ) {682		return false;683	}684	if ( $strict ) {685		$lastc = substr( $data, -1 );686		if ( ';' !== $lastc && '}' !== $lastc ) {687			return false;688		}689	} else {690		$semicolon = strpos( $data, ';' );691		$brace     = strpos( $data, '}' );692		// Either ; or } must exist.693		if ( false === $semicolon && false === $brace ) {694			return false;695		}696		// But neither must be in the first X characters.697		if ( false !== $semicolon && $semicolon < 3 ) {698			return false;699		}700		if ( false !== $brace && $brace < 4 ) {701			return false;702		}703	}704	$token = $data[0];705	switch ( $token ) {706		case 's':707			if ( $strict ) {708				if ( '"' !== substr( $data, -2, 1 ) ) {709					return false;710				}711			} elseif ( ! str_contains( $data, '"' ) ) {712				return false;713			}714			// Or else fall through.715		case 'a':716		case 'O':717		case 'E':718			return (bool) preg_match( "/^{$token}:[0-9]+:/s", $data );719		case 'b':720		case 'i':721		case 'd':722			$end = $strict ? '$' : '';723			return (bool) preg_match( "/^{$token}:[0-9.E+-]+;$end/", $data );724	}725	return false;726}