strcspn

useful for finding beginning of quotes and/or tags in a variable containing html.      $pos = strcspn($data, '<"\''); will find the first occurance of either the beginning of a tag, or a double- or single-quoted string.

this function can be used like strspn(), except while that can be used to compare a string with an allowed pattern, this one can be use to compare a string with a FORBIDDEN patternso, to know if any forbidden character has a position inside our string, we can use (not tested with backslashes)...<?php// LARGE VERSION$forbidden="\"\\?*:/@|<>";if (strlen($filename) != strcspn($filename,$forbidden)) {    echo "you cant create a file with that name!";}// SHORT VERSIONif (strlen($filename) - strcspn($filename,"\"\\?*:/@|<>")) {    echo "i told you, you cant create that file";}?>

When you use the third parameter remember that the function will return the number of characters it bypassed, which will *not* be the position in your source string.  It's a simple fix to just add your third parameter value to the function result to get the position in the first string where the scan stopped, but I didn't think of it at first.

It might not be clear from the example, thatstrcspn('abcdhelloabcd', 'abcd', -9, -5) == 4because it's only evaluating 'hell' which doesn't contain any mask, so returns strlen('hell').

strcspn() can also be thought of as analogous to the following regular expression:<?php// where ... represents the mask of characterspreg_match('/[^ ...]/', substr($subject, $start, $length) );?>By this analogy, strcspn() can be used in place of some regular expressions to match a pattern without the overhead of a regex engine -- for example, ways to verify if an input string represents a binary value:<?phppreg_match('/^[01]+$/i', $subject);// or...!preg_match('/[^01]/i', $subject);// ...or using strcspn()!strcspn($subject, '01');?>