PHP正则表达式和字符串匹配示例

// preg_match()
$pattern = '/hello/';
$string = 'hello world';

if (preg_match($pattern, $string)) {
    echo 'Match found!';
} else {
    echo 'Match not found.';
}
// 输出：Match found!

// preg_match_all()
$pattern = '/\d+/';
$string = 'The number is 12345';

if (preg_match_all($pattern, $string, $matches)) {
    echo 'Match found '.$matches[0][0].' times.';
} else {
    echo 'Match not found.';
}
// 输出：Match found 12345 times.

// preg_replace()
$pattern = '/world/';
$string = 'hello world';

$new_string = preg_replace($pattern, 'PHP', $string);

echo $new_string;
// 输出：hello PHP

// preg_split()
$pattern = '/\s+/';
$string = 'hello world';

$words = preg_split($pattern, $string);

print_r($words);
// 输出：Array([0] => hello [1] => world)

// strpos()
$needle = 'world';
$haystack = 'hello world';

if (strpos($haystack, $needle) !== false) {
    echo 'Match found!';
} else {
    echo 'Match not found.';
}
// 输出：Match found!

// strrpos()
$needle = 'world';
$haystack = 'hello world';

if (strrpos($haystack, $needle) !== false) {
    echo 'Match found!';
} else {
    echo 'Match not found.';
}
// 输出：Match found!

// substr()
$string = 'hello world';

$sub = substr($string, 6, 5);

echo $sub;
// 输出：world

// str_replace()
$needle = 'world';
$replacement = 'PHP';
$haystack = 'hello world';

$new_string = str_replace($needle, $replacement, $haystack);

echo $new_string;
// 输出：hello PHP