php 计算字符串个数

<?php
$str = "Hello, World!";
$char = "l";
$count = substr_count($str, $char);
echo "The character '$char' appears $count times in the string.";
?>

<?php
$str = "Hello, World! Hello!";
$substr = "Hello";
$count = substr_count($str, $substr);
echo "The substring '$substr' appears $count times in the string.";
?>

<?php
$str = "Hello, World! Hello!";
$pattern = "/Hello/";
$count = preg_match_all($pattern, $str, $matches);
echo "The pattern '$pattern' appears $count times in the string.";
?>

<?php
$str = "Hello, World! Hello!";
$pattern = preg_quote("Hello", '/');
$count = preg_match_all($pattern, $str, $matches);
echo "The pattern '$pattern' appears $count times in the string.";
?>