PHP正则表达式。 检查String是否仅包含字母

Question

In PHP, how do I check if a String contains only letters? I want to write an if statement that will return false if there is (white space, number, symbol) or anything else other than az and AZ .

My string must contain ONLY letters.

I thought I could do it this way, but I'm doing it wrong:

if( ereg("[a-zA-Z]+", $myString))
   return true;
else
   return false;

How do I find out if myString contains only letters?

Answer 1

Yeah this works fine. Thanks

if(myString.matches("^[a-zA-Z]+$"))

Answer 2

Never heard of ereg , but I'd guess that it will match on substrings.

In that case, you want to include anchors on either end of your regexp so as to force a match on the whole string:

"^[a-zA-Z]+$"

Also, you could simplify your function to read

return ereg("^[a-zA-Z]+$", $myString);

because the if to return true or false from what's already a boolean is redundant.

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Alternatively, you could match on any character that's not a letter, and return the complement of the result:

return !ereg("[^a-zA-Z]", $myString);

Note the ^ at the beginning of the character set, which inverts it. Also note that you no longer need the + after it, as a single "bad" character will cause a match.

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Finally... this advice is for Java because you have a Java tag on your question. But the $ in $myString makes it look like you're dealing with, maybe Perl or PHP? Some clarification might help.

Answer 3

Your code looks like PHP . It would return true if the string has a letter in it. To make sure the string has only letters you need to use the start and end anchors :

In Java you can make use of the matches method of the String class:

boolean hasOnlyLetters(String str) {
   return str.matches("^[a-zA-Z]+$");
}

In PHP the function ereg is deprecated now. You need to use the preg_match as replacement. The PHP equivalent of the above function is:

function hasOnlyLetters($str) {
   return preg_match('/^[a-z]+$/i',$str);
}

Answer 4

I'm going to be different and use Character.isLetter definition of what is a letter.

if (myString.matches("\\p{javaLetter}*"))

Note that this matches more than just [A-Za-z]* .

A character is considered to be a letter if its general category type, provided by Character.getType(ch) , is any of the following: UPPERCASE_LETTER, LOWERCASE_LETTER, TITLECASE_LETTER, MODIFIER_LETTER, OTHER_LETTER

Not all letters have case. Many characters are letters but are neither uppercase nor lowercase nor titlecase.

The \\p{javaXXX} character classes is defined in Pattern API .

Answer 5

或者，尝试检查它是否包含字母以外的任何内容：[^ A-Za-z]

Answer 6

The easiest way to do a "is ALL characters of a given type" is to check if ANY character is NOT of the type.

So if \\W denotes a non-character, then just check for one of those.