strrev
Generally speaking, linear searches are from start to end, not end to start - which makes sense from a human perspective. If you need to find strings in a string backwards, reverse your haystack and needle rather than manually chopping it up.
strripos
(PHP 5)
strripos — 文字列中で、特定の(大文字小文字を区別しない)文字列が最後に現れた位置を探す
説明
int strripos
( string
$haystack
, string $needle
[, int $offset = 0
] )
文字列 haystack の中で、
needle が最後に現れる位置を探します。
strrpos() と異なり、strripos() は大文字小文字を区別しません。
パラメータ
-
haystack -
検索を行う文字列。
-
needle -
needleが文字列でない場合は、 それを整数に変換し、その番号に対応する文字として扱います。 -
offset -
指定すると、文字列の開始位置からこの文字数だけ進んだところで検索を中止します。 負の値を指定すると、文字列の最後からこの文字数だけ戻ったところから逆向きに検索を開始します。
返り値
needle が見つかった位置を、
haystack 文字列の先頭 (offset の値とは無関係) からの相対位置で返します。
文字列の開始位置は 0 であり、1 ではないことに注意しましょう。
needle が見つからない場合は FALSE を返します。
例
例1 単純な strripos() の例
<?php
$haystack = 'ababcd';
$needle = 'aB';
$pos = strripos($haystack, $needle);
if ($pos === false) {
echo "ごめんなさい、($needle) が ($haystack) の中に見つかりませんでした。";
} else {
echo "おめでとう!\n";
echo "($needle) が最後に ($haystack) に現れた位置は ($pos) です。";
}
?>
上の例の出力は以下となります。
おめでとう! (aB) が最後に (ababcd) に現れた位置は (2) です。
add a note
User Contributed Notes
strripos
Anonymous
31-Aug-2010 03:05
admin at e-xxi dot net
08-Mar-2010 08:00
strripos() has very strange behaviour when you provide search position. For some reason it searches forward from the given position, instead of searching backward, that is more logical.
For example if you want to find instanse of $what, previous to the last, strripos($where, $what, $last_what_pos-1) will not wark as expected. It will return $last_what_pos again and again. And that has no sence at all.
To prevent this, I just used $prev_last_what_pos = strripos(substr($where,0,$last_what_pos), $what);
dimmav at in dot gr
25-Sep-2008 11:31
Suppose you just need a stripos function working backwards expecting that strripos does this job, you better use the following code of a custom function named strbipos:
<?php
function strbipos($haystack="", $needle="", $offset=0) {
// Search backwards in $haystack for $needle starting from $offset and return the position found or false
$len = strlen($haystack);
$pos = stripos(strrev($haystack), strrev($needle), $len - $offset - 1);
return ( ($pos === false) ? false : $len - strlen($needle) - $pos );
}
// Test
$body = "01234Xy7890XYz456xy90";
$str = "xY";
$len = strlen($body);
echo "TEST POSITIVE offset VALUES IN strbipos<br>";
for ($i = 0; $i < $len; $i++) {
echo "Search in [$body] for [$str] starting from offset [$i]: [" . strbipos($body, $str, $i) . "]<br>";
}
?>
Note that this function does exactly what it says and its results are different comparing to PHP 5 strripos function.
peev[dot]alexander at gmail dot com
20-Apr-2008 04:14
OK, I guess this will be the final function implementation for PHP 4.x versions ( my previous posts are invalid )
<?php
if(!function_exists("stripos")){
function stripos( $str, $needle, $offset = 0 ){
return strpos( strtolower( $str ), strtolower( $needle ), $offset );
}/* endfunction stripos */
}/* endfunction exists stripos */
if(!function_exists("strripos")){
function strripos( $haystack, $needle, $offset = 0 ) {
if( !is_string( $needle ) )$needle = chr( intval( $needle ) );
if( $offset < 0 ){
$temp_cut = strrev( substr( $haystack, 0, abs($offset) ) );
}
else{
$temp_cut = strrev( substr( $haystack, 0, max( ( strlen($haystack) - $offset ), 0 ) ) );
}
if( ( $found = stripos( $temp_cut, strrev($needle) ) ) === FALSE )return FALSE;
$pos = ( strlen( $haystack ) - ( $found + $offset + strlen( $needle ) ) );
return $pos;
}/* endfunction strripos */
}/* endfunction exists strripos */
?>
peev[dot]alexander at gmail dot com
23-Nov-2007 04:05
Oops, I forgot to return "false" if the needle is not found. Here is the proper function.
<?php
if(!function_exists("strripos")){
function strripos($haystack, $needle, $offset=0) {
if($offset<0){
$temp_cut = strrev( substr( $haystack, 0, abs($offset) ) );
}
else{
$temp_cut = strrev( substr( $haystack, $offset ) );
}
$pos = strlen($haystack) - (strpos($temp_cut, strrev($needle)) + $offset + strlen($needle));
if ($pos == strlen($haystack)) { $pos = 0; }
if(strpos($temp_cut, strrev($needle))===false){
return false;
}
else return $pos;
}/* endfunction strripos*/
}/* endfunction exists strripos*/
?>
peev[dot]alexander at gmail dot com
17-Oct-2007 07:23
I think you shouldn't underestimate the length of $needle in the search of THE FIRST POSITION of it's last occurrence in the string. I improved the posted function, with added support for offset. I think this is an exact copy of the real function:
<?php
if(!function_exists("strripos")){
function strripos($haystack, $needle, $offset=0) {
if($offset<0){
$temp_cut = strrev( substr( $haystack, 0, abs($offset) ) );
}
else{
$temp_cut = strrev( substr( $haystack, $offset ) );
}
$pos = strlen($haystack) - (strpos($temp_cut, strrev($needle)) + $offset + strlen($needle));
if ($pos == strlen($haystack)) { $pos = 0; }
return $pos;
}/* endfunction strripos*/
}/* endfunction exists strripos*/
?>
ElectroFox
02-Aug-2007 03:59
Sorry, I made that last post a bit prematurely. One more thing wrong with the simple php4 version is that it breaks if the string is not found. It should actually look like this:
<?php
if (function_exists('strripos') == false) {
function strripos($haystack, $needle) {
$pos = strlen($haystack) - strpos(strrev($haystack), strrev($needle));
if ($pos == strlen($haystack)) { $pos = 0; }
return $pos;
}
}
?>
Note, we now check to see if the $needle was found, and if it isn't, we return 0.
ElectroFox
02-Aug-2007 03:39
Actually, the above, "Simple way to implement this function in PHP 4" by Yanik Lupien, should be:
<?php
if (function_exists('strripos') == false) {
function strripos($haystack, $needle) {
return strlen($haystack) - strpos(strrev($haystack), strrev($needle));
}
}
?>
Note the reversal (<?php strrev($needle)?>) of the search string. This was left out in Yanik's example, and without it, you'll simply get the length of the haystack, as the forward string will not likely be found in the reversed haystack.
Thus; if we reverse the haystack, any instance of the search string ($needle) therein will also be reversed, so we must reverse it to look for it. :)
Yanik Lupien
03-Jul-2007 12:47
Simple way to implement this function in PHP 4
<?php
if (function_exists('strripos') == false) {
function strripos($haystack, $needle) {
return strlen($haystack) - strpos(strrev($haystack), $needle);
}
}
?>
aidan at php dot net
30-May-2004 12:36
This functionality is now implemented in the PEAR package PHP_Compat.
More information about using this function without upgrading your version of PHP can be found on the below link:
http://pear.php.net/package/PHP_Compat