Detect Blank with Regex - regex

Question

I am using the following regex to check a name field for invalid characters...
if (!preg_match("/^[a-zA-Z ]*$/",$mystring))
Is there a way to also detect if the string is blank using regex? Or am I better off doing that using PHP?

Answer 1

You can just do a simple check without a regex:
if( $string == "") //do something
or
if(strlen($string) == 0) //do something
or
if(strlen(trim($string)) == 0) //do something

Answer 2

Or,
<?php
$str = "\r\n\t\0 ";
if (trim($str) == "") {
echo "This string is blank";
}
Trimming the string of any white space characters, including one or more spaces and then comparing the result to an empty string will detect a blank string. The advantage here is that you need only use one function, namely trim.
One may certainly use trim() and strlen() together to achieve the same result, but that requires two functions instead of one.
Using strlen() without trimming the input $str could lead to accepting a "blank" line, as follows:
<?php
$content = 'Content: ';
$str = " \r\n\t\0 ";
if ( strlen( $str ) == 0) {
echo 'blank line',"\n";
}
else
{
$content .= $str;
}
echo $content;
By not trimming the string of any white space characters the string length in this case is six but the a visibly blank $str gets appended to $content.