[SOLVED] how can I check for illegal characters in a string?

[frijole]

I would like to check a string to see if the username has any illegal characters, i.e. anything that is not a letter or a number, Any ideas?

[p2grace]

This should do the trick:

 

<?php
$text = "test123";
if (!ereg('[^A-Za-z0-9]', $text)) {
echo "contains only letters and numbers";
}else{
        echo "contains invalid characters.";
}
?>

[frijole]

the ereg() function returns the length of string? I read the manual and i do not understand how the !ereg() argument works? can anyone clarify this for me?