strrpos
(PHP 4, PHP 5)
strrpos — Возвращает позицию последнего вхождения символа
Описание
Возвращает позицию последнего вхождения needle в строку haystack . В PHP 4 используется только первый символ строки needle .
Если подстрока needle не найдена, возвращает FALSE.
Эта функция может возвращать как логическое значение FALSE, так и не относящееся к логическому типу значение, которое приводится к FALSE, например, 0 или "". За более подробной информации обратитесь к разделу Булев тип. Используйте оператор === для проверки значения, возвращаемого этой функцией.
Если needle не является строкой, он приводится к целому и трактуется как код символа.
Замечание: Начиная с PHP 5.0.0, необязательный аргумент offset позволяет указать, с какого по счету символа строки haystack начинать поиск. Отрицательное значение предписывает прекратить поиск при достижении определенной позиции до конца строки.
Замечание: Начиная с PHP 5.0.0 needle используется полностью (а не только первый символ).
См. также описание функций strpos(), strripos(), strrchr(), substr(), stristr() и strstr().
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Коментарии
Maybe I'm the only one who's bothered by it, but it really bugs me when the last line in a paragraph is a single word. Here's an example to explain what I don't like:
The quick brown fox jumps over the lazy
dog.
So that's why I wrote this function. In any paragraph that contains more than 1 space (i.e., more than two words), it will replace the last space with ' '.
<?php
function no_orphans($TheParagraph) {
if (substr_count($TheParagraph," ") > 1) {
$lastspace = strrpos($TheParagraph," ");
$TheParagraph = substr_replace($TheParagraph," ",$lastspace,1);
}
return $TheParagraph;
}
?>
So, it would change "The quick brown fox jumps over the lazy dog." to "The quick brown fox jumps over the lazy dog." That way, the last two words will always stay together.
I was looking for the equivalent of Java's lastIndexOf(). I couldn't find it so I wrote this:
<?php
/*
Method to return the last occurrence of a substring within a
string
*/
function last_index_of($sub_str,$instr) {
if(strstr($instr,$sub_str)!="") {
return(strlen($instr)-strpos(strrev($instr),$sub_str));
}
return(-1);
}
?>
It returns the numerical index of the substring you're searching for, or -1 if the substring doesn't exist within the string.
refering to the comment and function about lastIndexOf()...
It seemed not to work for me the only reason I could find was the haystack was reversed and the string wasnt therefore it returnt the length of the haystack rather than the position of the last needle... i rewrote it as fallows:
<?php
function strlpos($f_haystack,$f_needle) {
$rev_str = strrev($f_needle);
$rev_hay = strrev($f_haystack);
$hay_len = strlen($f_haystack);
$ned_pos = strpos($rev_hay,$rev_str);
$result = $hay_len - $ned_pos - strlen($rev_str);
return $result;
}
?>
this one fallows the strpos syntax rather than java's lastIndexOf.
I'm not positive if it takes more resources assigning all of those variables in there but you can put it all in return if you want, i dont care if i crash my server ;).
~SILENT WIND OF DOOM WOOSH!
I should have looked here first, but instead I wrote my own version of strrpos that supports searching for entire strings, rather than individual characters. This is a recursive function. I have not tested to see if it is more or less efficient than the others on the page. I hope this helps someone!
<?php
//Find last occurance of needle in haystack
function str_rpos($haystack, $needle, $start = 0){
$tempPos = strpos($haystack, $needle, $start);
if($tempPos === false){
if($start == 0){
//Needle not in string at all
return false;
}else{
//No more occurances found
return $start - strlen($needle);
}
}else{
//Find the next occurance
return str_rpos($haystack, $needle, $tempPos + strlen($needle));
}
}
?>
this could be, what derek mentioned:
<?
function cut_last_occurence($string,$cut_off) {
return strrev(substr(strstr(strrev($string), strrev($cut_off)),strlen($cut_off)));
}
// example: cut off the last occurence of "limit"
$str = "select delta_limit1, delta_limit2, delta_limit3 from table limit 1,7";
$search = " limit";
echo $str."\n";
echo cut_last_occurence($str,"limit");
?>
What the heck, I thought I'd throw another function in the mix. It's not pretty but the following function counts backwards from your starting point and tells you the last occurrance of a mixed char string:
<?php
function strrposmixed ($haystack, $needle, $start=0) {
// init start as the end of the str if not set
if($start == 0) {
$start = strlen($haystack);
}
// searches backward from $start
$currentStrPos=$start;
$lastFoundPos=false;
while($currentStrPos != 0) {
if(!(strpos($haystack,$needle,$currentStrPos) === false)) {
$lastFoundPos=strpos($haystack,$needle,$currentStrPos);
break;
}
$currentStrPos--;
}
if($lastFoundPos === false) {
return false;
} else {
return $lastFoundPos;
}
}
?>
Function like the 5.0 version of strrpos for 4.x.
This will return the *last* occurence of a string within a string.
function strepos($haystack, $needle, $offset=0) {
$pos_rule = ($offset<0)?strlen($haystack)+($offset-1):$offset;
$last_pos = false; $first_run = true;
do {
$pos=strpos($haystack, $needle, (intval($last_pos)+(($first_run)?0:strlen($needle))));
if ($pos!==false && (($offset<0 && $pos <= $pos_rule)||$offset >= 0)) {
$last_pos = $pos;
} else { break; }
$first_run = false;
} while ($pos !== false);
if ($offset>0 && $last_pos<$pos_rule) { $last_pos = false; }
return $last_pos;
}
If my math is off, please feel free to correct.
- A positive offset will be the minimum character index position of the first character allowed.
- A negative offset will be subtracted from the total length and the position directly before will be the maximum index of the first character being searched.
returns the character index ( 0+ ) of the last occurence of the needle.
* boolean FALSE will return no matches within the haystack, or outside boundries specified by the offset.
I was immediatley pissed when i found the behaviour of strrpos ( shouldnt it be called charrpos ?) the way it is, so i made my own implement to search for strings.
<?
function proper_strrpos($haystack,$needle){
while($ret = strrpos($haystack,$needle))
{
if(strncmp(substr($haystack,$ret,strlen($needle)),
$needle,strlen($needle)) == 0 )
return $ret;
$haystack = substr($haystack,0,$ret -1 );
}
return $ret;
}
?>
I needed to remove last directory from an path, and came up with this solution:
<?php
$path_dir = "/my/sweet/home/";
$path_up = substr( $path_dir, 0, strrpos( $path_dir, '/', -2 ) )."/";
echo $path_up;
?>
Might be helpful for someone..
RE: hao2lian
There are a lot of alternative - and unfortunately buggy - implementations of strrpos() (or last_index_of as it was called) on this page. This one is a slight modifiaction of the one below, but it should world like a *real* strrpos(), because it returns false if there is no needle in the haystack.
<?php
function my_strrpos($haystack, $needle) {
$index = strpos(strrev($haystack), strrev($needle));
if($index === false) {
return false;
}
$index = strlen($haystack) - strlen($needle) - $index;
return $index;
}
?>
Very handy to get a file extension:$this->data['extension'] = substr($this->data['name'],strrpos($this->data['name'],'.')+1);
The "find-last-occurrence-of-a-string" functions suggested here do not allow for a starting offset, so here's one, tried and tested, that does:
function my_strrpos($haystack, $needle, $offset=0) {
// same as strrpos, except $needle can be a string
$strrpos = false;
if (is_string($haystack) && is_string($needle) && is_numeric($offset)) {
$strlen = strlen($haystack);
$strpos = strpos(strrev(substr($haystack, $offset)), strrev($needle));
if (is_numeric($strpos)) {
$strrpos = $strlen - $strpos - strlen($needle);
}
}
return $strrpos;
}
In strrstr function in php 4 there is also no offset.<?
// by Shimon Doodkin
function chrrpos($haystack, $needle, $offset=false)
{
$needle=$needle[0];
$l=strlen($haystack);
if($l==0) return false;
if($offset===false) $offset=$l-1;
else
{
if($offset>$l) $offset=$l-1;
if($offset<0) return false;
}
for(;$offset>0;$offset--)
if($haystack[$offset]==$needle)
return $offset;
return false;
}
?>
<?php
###################################################
#
# DESCRIPTION:
# This function returns the last occurance of a string,
# rather than the last occurance of a single character like
# strrpos does. It also supports an offset from where to
# start the searching in the haystack string.
#
# ARGS:
# $haystack (required) -- the string to search upon
# $needle (required) -- the string you are looking for
# $offset (optional) -- the offset to start from
#
# RETURN VALS:
# returns integer on success
# returns false on failure to find the string at all
#
###################################################
function strrpos_string($haystack, $needle, $offset = 0)
{
if(trim($haystack) != "" && trim($needle) != "" && $offset <= strlen($haystack))
{
$last_pos = $offset;
$found = false;
while(($curr_pos = strpos($haystack, $needle, $last_pos)) !== false)
{
$found = true;
$last_pos = $curr_pos + 1;
}
if($found)
{
return $last_pos - 1;
}
else
{
return false;
}
}
else
{
return false;
}
}
?>
Returns the filename's string extension, else if no extension found returns false.Example: filename_extension('some_file.mp3'); // mp3
Faster than the pathinfo() analogue in two times.
<?php
function filename_extension($filename) {
$pos = strrpos($filename, '.');
if($pos===false) {
return false;
} else {
return substr($filename, $pos+1);
}
}
?>
<?php/*******
** Maybe the shortest code to find the last occurence of a string, even in php4
*******/
function stringrpos($haystack,$needle,$offset=NULL)
{
return strlen($haystack)
- strpos( strrev($haystack) , strrev($needle) , $offset)
- strlen($needle);
}
// @return -> chopped up for readability.
?>
Function to truncate a string
Removing dot and comma
Adding ... only if a is character found
function TruncateString($phrase, $longueurMax = 150) {
$phrase = substr(trim($phrase), 0, $longueurMax);
$pos = strrpos($phrase, " ");
$phrase = substr($phrase, 0, $pos);
if ((substr($phrase,-1,1) == ",") or (substr($phrase,-1,1) == ".")) {
$phrase = substr($phrase,0,-1);
}
if ($pos === false) {
$phrase = $phrase;
}
else {
$phrase = $phrase . "...";
}
return $phrase;
}
To begin, i'm sorry for my English.
So, I needed of one function which gives me the front last position of a character.
Then I said myself that it should be better to make one which gives the "N" last position.
$return_context = "1173120681_0__0_0_Mijsoot_Thierry";
// Here i need to find = "Mijsoot_Thierry"
//echo $return_context."<br />";// -- DEBUG
function findPos($haystack,$needle,$position){
$pos = strrpos($haystack, $needle);
if($position>1){
$position --;
$haystack = substr($haystack, 0, $pos);
$pos = findPos($haystack,$needle,$position);
}else{
// echo $haystack."<br />"; // -- DEBUG
return $pos;
}
return $pos;
}
var_dump(findPos($return_context,"_",2)); // -- TEST
Full strpos() functionality, by yours truly.
<?php
function conforming_strrpos($haystack, $needle, $offset = 0)
{
# Why does strpos() do this? Anyway...
if(!is_string($needle)) $needle = ord(intval($needle));
$haystack = strval($haystack);
# Parameters
$hlen = strlen($haystack);
$nlen = strlen($needle);
# Come on, this is a feature too
if($nlen == 0)
{
trigger_error(__FUNCTION__.'(): Empty delimiter.', E_USER_WARNING);
return false;
}
$offset = intval($offset);
$hrev = strrev($haystack);
$nrev = strrev($needle);
# Search
$pos = strpos($hrev, $nrev, $offset);
if($pos === false) return false;
else return $hlen - $nlen - $pos;
}
?>
Note that $offset is evaluated from the end of the string.
Also note that conforming_strrpos() performs some five times slower than strpos(). Just a thought.
The documentation for 'offset' is misleading.
It says, "offset may be specified to begin searching an arbitrary number of characters into the string. Negative values will stop searching at an arbitrary point prior to the end of the string."
This is confusing if you think of strrpos as starting at the end of the string and working backwards.
A better way to think of offset is:
- If offset is positive, then strrpos only operates on the part of the string from offset to the end. This will usually have the same results as not specifying an offset, unless the only occurences of needle are before offset (in which case specifying the offset won't find the needle).
- If offset is negative, then strrpos only operates on that many characters at the end of the string. If the needle is farther away from the end of the string, it won't be found.
If, for example, you want to find the last space in a string before the 50th character, you'll need to do something like this:
strrpos($text, " ", -(strlen($text) - 50));
If instead you used strrpos($text, " ", 50), then you would find the last space between the 50th character and the end of the string, which may not have been what you were intending.
Here is a simple function to find the position of the next occurrence of needle in haystack, but searching backwards (lastIndexOf type function):
//search backwards for needle in haystack, and return its position
function rstrpos ($haystack, $needle, $offset){
$size = strlen ($haystack);
$pos = strpos (strrev($haystack), $needle, $size - $offset);
if ($pos === false)
return false;
return $size - $pos;
}
Note: supports full strings as needle
<?php
$pos = strlen(string $haystack) - strpos (strrev(string $haystack), strrev(string $needle)) - strlen(string $needle);
?>
If in the needle there is more than one character then in php 4 we can use the above statement for finding the position of last occurrence of a substring in a string instead of strrpos. Because in php 4 strrpos uses the first character of the substring.
eg :
<?php
$haystack = "you you you you you";
$needle = "you";
$pos1 = strlen($haystack) - strpos (strrev($haystack), strrev($needle)) - strlen($needle);
echo $pos1 . "<br>";
$pos2 strrpos($haystack, $needle);
echo $pos2 . "<br>";
?>
I needed to check if a variable that contains a generated folder name based on user input had a trailing slash.
This did the trick:
<?php
// Detect and remove a trailing slash
$root_folder = ((strrpos($root_folder, '/') + 1) == strlen($root_folder)) ? substr($root_folder, 0, - 1) : $root_folder;
?>
I've got a simple method of performing a reverse strpos which may be of use. This version I have treats the offset very simply:
Positive offsets search backwards from the supplied string index.
Negative offsets search backwards from the position of the character that many characters from the end of the string.
Here is an example of backwards stepping through instances of a string with this function:
<?php
function backwardStrpos($haystack, $needle, $offset = 0){
$length = strlen($haystack);
$offset = ($offset > 0)?($length - $offset):abs($offset);
$pos = strpos(strrev($haystack), strrev($needle), $offset);
return ($pos === false)?false:( $length - $pos - strlen($needle) );
}
$pos = 0;
$count = 0;
echo "Test1<br/>";
while(($pos = backwardStrpos("012340567890", "0", $pos)) !== false){
echo $pos."<br/>";
$pos--;
if($pos < 0){
echo "Done<br/>";break;
}
}
echo "---===---<br/>\nTest2<br/>";
echo backwardStrpos("12341234", "1", 2)."<br/>";
echo backwardStrpos("12341234", "1", -2);
?>
Outputs:
Test1
11
5
0
Done
---===---
Test2
0
4
With Test2 the first line checks from the first 3 in "12341234" and runs backwards until it finds a 1 (at position 0)
The second line checks from the second 2 in "12341234" and seeks towards the beginning for the first 1 it finds (at position 4).
This function is useful for php4 and also useful if the offset parameter in the existing strrpos is equally confusing to you as it is for me.
This seems to behave like the exact equivalent to the PHP 5 offset parameter for a PHP 4 version.
<?php
function strrpos_handmade($haystack, $needle, $offset = 0){
if($offset === 0) return strrpos($haystack, $needle);
$length = strlen($haystack);
$size = strlen($needle);
if($offset < 0) {
$virtual_cut = $length+$offset;
$haystack = substr($haystack, 0, $virtual_cut+$size);
$ret = strrpos($haystack, $needle);
return $ret > $virtual_cut ? false : $ret;
} else {
$haystack = substr($haystack, $offset);
$ret = strrpos($haystack, $needle);
return $ret === false ? $ret : $ret+$offset;
}
}
?>
$offset is very misleading, here is my understanding:
function mystrrpos($haystack, $needle, $offset = 0) {
if ($offset == 0) {
return strrpos ($haystack, $needle);
} else {
return strrpos (substr($haystack, 0, $offset), $needle);
}
}
i wanted to find a leading space BEFORE a hyphen
Crude Oil (Dec) 51.00-56.00
so I had to find the position of the hyphen
then subtract that position from the length of the string (to make it a negative number)
and then walk left toward the beginning of the string, looking for the first space before the hyphen
ex:
$str_position_hyphen = strpos($line_new,"-",$str_position_spread);
$line_new_length = strlen($line_new);
$str_position_hyphen_from_end = $str_position_hyphen - $line_new_length;
echo "hyphen position from end = " . $str_position_hyphen_from_end . "<br />\n";
$str_position_space_before_hyphen = strrpos($line_new, " ", $str_position_hyphen_from_end);
echo "*** previous space= " . $str_position_space_before_hyphen . "<br />\n";
$line_new = substr_replace($line_new, ",", $str_position_space_before_hyphen, 1 );
echo $line_new . "<br /><br />\n";
Ten years on, Brian's note is still a good overview of how offsets work, but a shorter and simpler summary is:
strrpos($x, $y, 50); // 1: this tells strrpos() when to STOP, counting from the START of $x
strrpos($x, $y, -50); // 2: this tells strrpos() when to START, counting from the END of $x
Or to put it another way, a positive number lets you search the rightmost section of the string, while a negative number lets you search the leftmost section of the string.
Both these variations are useful, but picking the wrong one can cause some highly confusing results!
The description of offset is wrong. Here’s how it works, with supporting examples.
Offset effects both the starting point and stopping point of the search. The direction is always right to left. (The description wrongly says PHP searches left to right when offset is positive.)
Here’s how it works:
When offset is positive, PHP searches right to left from the end of haystack to offset. This ignores the left side of haystack.
When offset is negative, PHP searches right to left, starting offset bytes from the end, to the start of haystack. This ignores the right side of haystack.
Example 1:
$foo = ‘aaaaaaaaaa’;
var_dump(strrpos($foo, 'a', 5));
Result: int(10)
Example 2:
$foo = "aaaaaa67890";
var_dump(strrpos($foo, 'a', 5));
Result: int(5)
Conclusion: When offset is positive, PHP searches right to left from the end of haystack.
Example 3:
$foo = "aaaaa567890";
var_dump(strrpos($foo, 'a', 5));
Result: bool(false)
Conclusion: When offset is positive, PHP stops searching at offset.
Example 4:
$foo = ‘aaaaaaaaaa’;
var_dump(strrpos($foo, 'a', -5));
Result: int(6)
Conclusion: When offset is negative, PHP searches right to left, starting offset bytes from the end.
Example 5:
$foo = "a234567890";
var_dump(strrpos($foo, 'a', -5));
Result: int(0)
Conclusion: When offset is negative, PHP searches right to left, all the way to the start of haystack.
There is a lot of confusion around how $offset works and I feel it's really quite simple.
If $offset is positive, the operation ignores the first $offset characters of the haystack.
If $offset is negative, the operation ignores the last $offset-1 characters of the haystack (don't ask why -1...).
To understand this instinctively, just imagine the characters being replaced with invalid symbols. Here's an example:
<?php
$hackstack = '0123456789';
// Search the entire sequence 0123456789
var_dump(strrpos($hackstack, '0')); // int(0)
var_dump(strrpos($hackstack, '9')); // int(9)
// Only search ##23456789
var_dump(strrpos($hackstack, '1', 2)); // bool(false)
var_dump(strrpos($hackstack, '2', 2)); // int(2)
// Only search 0123456###
var_dump(strrpos($hackstack, '6', -4)); // int(6)
var_dump(strrpos($hackstack, '7', -4)); // bool(false)
?>