正则表达式为2个字母，后跟4位数字 [英] Regex for 2 letters followed by 4 digits

问题描述

字符串应以"S2"开头，后跟任意4位数字.

The string should begin with "S2" followed by any 4 digits.

匹配的字符串是"S20165".

A matching string is "S20165".

我正在尝试以下代码，但是即使有5或6位数字，它也始终会回显OK.

I'm trying with the following code, but it always echos OK even when there are 5 or 6 digits.

$string='S20104';
if(preg_match('/S2[0-9]{4}/', $string)){
    echo 'OK';
}
else{
    echo 'NOT OK';
}

推荐答案

您必须使用锚点:

/^S2[0-9]{4}$/

^匹配字符串的开头，而$匹配字符串的结尾，因此这将确保您检查完整的字符串，而不仅仅是子字符串.

^ matches the start of the string and $ matches the end of the string, so this will make sure that you check the complete string and not just a substring.

您也可以使用\d代替[0-9].在PHP中，只要您不使用'u'模式修饰符，preg *函数不支持Unicode，因此两者是等效的.

You can also use \d instead of [0-9]. In PHP, as long as you do not use the 'u' pattern modifier, preg* functions are not Unicode aware, so the two are equivalent.

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