超越PHP - Exceed PHP: strrpos

Description

int strrpos ( string haystack, string needle [, int offset])

Returns the numeric position of the last occurrence of needle in the haystack string. Note that the needle in this case can only be a single character in PHP 4. If a string is passed as the needle, then only the first character of that string will be used.

If needle is not found, returns FALSE.

It is easy to mistake the return values for "character found at position 0" and "character not found". Here's how to detect the difference:


<?php



// in PHP 4.0b3 and newer:

$pos = strrpos($mystring, "b");

if ($pos === false) { // note: three equal signs

    // not found...

}



// in versions older than 4.0b3:

$pos = strrpos($mystring, "b");

if (is_bool($pos) && !$pos) {

    // not found...

}

?>

If needle is not a string, it is converted to an integer and applied as the ordinal value of a character.

注: As of PHP 5.0.0 offset may be specified to begin searching an arbitrary number of characters into the string. Negative values will stop searching at an arbitrary point prior to the end of the string.

注: The needle may be a string of more than one character as of PHP 5.0.0.

add a note User Contributed Notes
strrpos

derek at slashview dot com
02-Feb-2002 08:06

To find the position of the start of the last occurence of a string, we can
do this:
$pos=strlen($haystack) - (strpos(strrev($haystack),
strrev($needle)) + strlen($needle));
The idea is to reverse both $needle
and $haystack, use strpos to find the first occurence of $needle in
$haystack, then count backwards by the length of $needle. Finally, subtract
$pos from length of $haystack. A lot easier to figure out if you use a test
string to visualize it.  :)

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