strcspn

legacyprog at routinz dot net (2010-12-09 19:20:08)

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.

Anonymous (2009-10-16 10:55:56)

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

// ...or using strcspn()
!strcspn($subject, '01');
?>

Dmitry Mazur (2009-03-04 10:17:35)

The second parameter simply is the set of the "stop"-characters.
In other words, this function will return the index (starting from 0) of a first occurence of the stop-character.

PHP at NospamImmortalSoFar dot com (2006-10-07 18:31:23)

Also useful for breaking down expressions - for example parsing SQL: values ('this', fn("that,)()", 4))
$sep = strcspn ($list, "'\"`"); // Start of quoted string
$list = substr ($list, $sep);
$find = substr ($list, 0, 1);
while (($sep = strpos ($list, $find, $sep+1)) > 0 && substr ($list, $sep-1, 1) == '\\')
{}
// $sep now spans the entire string, regardless of embedded quotes
Once the strings have been removed, an expression can then be parsed for commas and brackets without worrying about them:
while ($out != '')
{
$sep = strcspn ($list, "(),"); // Next seperator
...
}

AT-HE (at_he AT hotmai1 DOT com) (2005-12-27 02:07:12)

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 pattern

so, 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 VERSION
if (strlen($filename) - strcspn($filename,"\"\\?*:/@|<>")) {
    echo "i told you, you cant create that file";
}
?>

maskedcoder at hotmail dot com (2005-10-10 16:13:50)

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.