如何防止[a-z]类型的正则表达式匹配控制字符

Question

recently I've been using [a-z] class range regexp in php. I don't know why, but instead of matching only a to z chars, it also matches control characters. Exemple:

preg_match("#^[a-z]{0,3}$#", "aa
")

is returning 1. (I'm on php 5.6). I would like to prevent the controls characters matched. I've done a few tests with [:^cntrl:] without much succcess. Could someone help me please. Thanks in advance.

Answer 1

The $ anchor may match at the end of the string, or before a final newline in a string.

Use a /D PCRE_DOLLAR_ENDONLY modifier:

preg_match("#^[a-z]{0,3}$#D", "aa
")
                         ^

Or \z anchor that matches at the very end of the string:

preg_match("#^[a-z]{0,3}\z#", "aa
")

PHP test:

echo preg_match("#^[a-z]{0,3}$#", "aa
");  // => 1
echo preg_match("#^[a-z]{0,3}$#D", "aa
"); // => 0
echo preg_match("#^[a-z]{0,3}\z#", "aa
"); // => 0