alnum Character Class in Regular expression
What is [[:alnum:]] Character Class in regex?
Explanation
The [[:alnum:]] character class represents alphabetic and numeric characters, and it is same as using [a-zA-Z0-9] in regular expression.
<?php
$org = 'AAA**&18';
$det = ereg_replace("[[:alnum:]]","@",$org);
echo $det;
?> Result :
@@@**&@@
In the above regex example the character class "[[:alnum:]]" is used along with the metacharacter "^",which specifies to match the begining of the string, since the string has the number "1" in the beginning its matched.
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
$str = "wew436*3631";
if ( $str =~ /[^[:alnum:]]/ )
{print "Character other than alphanumeric!";}
else
{print "Only alphanumeric characters!";} Result :
Character other than alphanumeric!
In the above example the metacharacter "^" refers the begining of the string, but here its used like "/[^[:alnum:]]/" which means "NOT" a alphanumeric character. Since the string has a "*" it matches as it not a alphanumeric character.
PHP Example:
<?php
$org = 'AAA**&18';
$det = ereg_replace("[[:alnum:]]","@",$org);
echo $det;
?>
@@@**&@@
In the above regex example the character class "[[:alnum:]]" is used along with the metacharacter "^",which specifies to match the begining of the string, since the string has the number "1" in the beginning its matched.
Perl Example:
#! C:programfilesperlbinperl
print "content-type: text/htmlnn";
$str = "wew436*3631";
if ( $str =~ /[^[:alnum:]]/ )
{print "Character other than alphanumeric!";}
else
{print "Only alphanumeric characters!";}
Character other than alphanumeric!
In the above example the metacharacter "^" refers the begining of the string, but here its used like "/[^[:alnum:]]/" which means "NOT" a alphanumeric character. Since the string has a "*" it matches as it not a alphanumeric character.
