在php preg_match中使用"*"或"？"有区别吗？或者有一个例子吗？
<?php
// the string to match against
$string = 'The cat sat on the matthew';
// matches the letter "a" followed by zero or more "t" characters
echo preg_match("/at*/", $string);
// matches the letter "a" followed by a "t" character that may or may not be present
echo preg_match("/at?/", $string);
*匹配0个或多个
?匹配0或1
在特定测试的上下文中，您无法区分差异，因为*和?匹配没有锚定或后面没有任何内容——它们都将匹配任何包含a的字符串，无论后面是否跟有t。
如果匹配字符后有，则差异很重要，例如：
echo preg_match("/at*z/", "attz"); // true
echo preg_match("/at?z/", "attz"); // false - too many "t"s
而你的：
echo preg_match("/at*/", "attz"); // true - 0 or more
echo preg_match("/at?/", "attz"); // true - but it stopped after the
// first "t" and ignored the second
// matches the letter "a" followed by zero or more "t" characters
// matches the letter "a" followed by a "t" character that may or may not be present
来源：你