Using regular expressions

What is wrong with this regexp? I need it to make $name to be letter-num开发者_高级运维ber only. Now it doens't seem to work at all.

 if (!preg_match("/^[A-Za-z0-9]$/",$name)) {
  $e[]="name must contain only letters or numbers";
 }

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You need a quantifier otherwise it will only allow one character. For example, to require that there must be one or more characters use +:

/^[A-Za-z0-9]+$/

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Your regular expression does only describe one single character. Either use a quantifier like + to allow that [A-Za-z0-9] is being repeated one or more times:

if (!preg_match("/^[A-Za-z0-9]+$/",$name))

Or you can inverse your expression and look for characters that are not alphanumeric ([^A-Za-z0-9] is the complement of [A-Za-z0-9]):

if (preg_match("/[^A-Za-z0-9]/",$name))

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Don't forget to look at other functions which will do what you want without the overhead of regexes. In this case, you could use ctype_alnum.

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When you don't exactly know what your expression does, sometimes it helps to test it with a tool. You could try maybe Regex Coach: http://www.weitz.de/regex-coach/ :)