问题描述
好的，所以我希望用户能够输入 A-Z 中的每个字符和 0-9 中的每个数字，但我不希望他们输入特殊字符".
Alright, so I want the user to be able to enter every character from A-Z and every number from 0-9, but I don't want them entering "special characters".
代码:
if (preg_match("/^[a-zA-Z0-9]$/", $user_name)) {
#Stuff
}
它如何检查给定的所有字符，然后检查它们是否匹配?我已经尝试过 preg_match_all()，但老实说我并没有真正理解它.
How is it possible for it to check all of the characters given, and then check if those were matched? I've tried preg_match_all(), but I didn't honestly understand much of it.
就像用户输入FaiL65Mal"一样，我希望它允许并继续.但是如果他们输入Fail{]^7(,"，我希望它出现错误.
Like if a user entered "FaiL65Mal", I want it to allow it and move on. But if they enter "Fail{]^7(,", I want it to appear with an error.
推荐答案
您只需要在正则表达式中添加一个量词:
You just need a quantifier in your regex:
零个或多个字符*:
/^[a-zA-Z0-9]*$/
一个或多个字符+:
/^[a-zA-Z0-9]+$/
您的正则表达式只会匹配一个字符串，它只包含一个字母或数字字符.您需要上述零个或多个或一个或多个选项之一，具体取决于您是要允许还是拒绝空字符串.
Your regex as is will only match a string with exactly one character that is either a letter or number. You want one of the above options for zero or more or one or more, depending on if you want to allow or reject the empty string.
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