PHP - 确保字符串没有空格

Question

如何检查PHP字符串是否包含任何空格？我想检查是否有空格,然后回显错误消息,如果为true

if(strlen($username) == whitespace ){

                echo "<center>Your username must not contain any whitespace</center>";

Answer 1

if ( preg_match('/\s/',$username) ) ....