strpos() with multiple needles? - php

Question

I am looking for a function like strpos() with two significant differences:
To be able to accept multiple needles. I mean thousands of needles at ones.
To search for all occurrences of the needles in the haystack and to return an array of starting positions.
Of course it has to be an efficient solution not just a loop through every needle. I have searched through this forum and there were similar questions to this one, like:
Using an array as needles in strpos
Define multiple needles using stripos
Can't search an array in PHP in_array for the presence of multiple needles
but nether of them was what I am looking for. I am using strpos just to illustrate my question better, probably something entirely different has to be used for this purpose.
I am aware of Zend_Search_Lucene and I am interested if it can be used to achieve this and how (just the general idea)?
Thanks a lot for Your help and time!

Answer 1

try preg match for multiple
if (preg_match('/word|word2/i', $str))
Checking for multiple strpos values

Answer 2

Here's some sample code for my strategy:
function strpos_array($haystack, $needles, $offset=0) {
$matches = array();
//Avoid the obvious: when haystack or needles are empty, return no matches
if(empty($needles) || empty($haystack)) {
return $matches;
}
$haystack = (string)$haystack; //Pre-cast non-string haystacks
$haylen = strlen($haystack);
//Allow negative (from end of haystack) offsets
if($offset < 0) {
$offset += $heylen;
}
//Use strpos if there is no array or only one needle
if(!is_array($needles)) {
$needles = array($needles);
}
$needles = array_unique($needles); //Not necessary if you are sure all needles are unique
//Precalculate needle lengths to save time
foreach($needles as &$origNeedle) {
$origNeedle = array((string)$origNeedle, strlen($origNeedle));
}
//Find matches
for(; $offset < $haylen; $offset++) {
foreach($needles as $needle) {
list($needle, $length) = $needle;
if($needle == substr($haystack, $offset, $length)) {
$matches[] = $offset;
break;
}
}
}
return($matches);
}
I've implemented a simple brute force method above that will work with any combination of needles and haystacks (not just words). For possibly faster algorithms check out:
Aho–Corasick string matching algorithm
Other Solution
function strpos_array($haystack, $needles, $theOffset=0) {
$matches = array();
if(empty($haystack) || empty($needles)) {
return $matches;
}
$haylen = strlen($haystack);
if($theOffset < 0) { // Support negative offsets
$theOffest += $haylen;
}
foreach($needles as $needle) {
$needlelen = strlen($needle);
$offset = $theOffset;
while(($match = strpos($haystack, $needle, $offset)) !== false) {
$matches[] = $match;
$offset = $match + $needlelen;
if($offset >= $haylen) {
break;
}
}
}
return $matches;
}

Answer 3

I know this doesn't answer the OP's question but wanted to comment since this page is at the top of Google for strpos with multiple needles. Here's a simple solution to do so (again, this isn't specific to the OP's question - sorry):
$img_formats = array('.jpg','.png');
$missing = array();
foreach ( $img_formats as $format )
if ( stripos($post['timer_background_image'], $format) === false ) $missing[] = $format;
if (count($missing) == 2)
return array("save_data"=>$post,"error"=>array("message"=>"The background image must be in a .jpg or .png format.","field"=>"timer_background_image"));
If 2 items are added to the $missing array that means that the input doesn't satisfy any of the image formats in the $img_formats array. At that point you know that you can return an error, etc. This could easily be turned into a little function:
function m_stripos( $haystack = null, $needles = array() ){
//return early if missing arguments
if ( !$needles || !$haystack ) return false;
// create an array to evaluate at the end
$missing = array();
//Loop through needles array, and add to $missing array if not satisfied
foreach ( $needles as $needle )
if ( stripos($haystack, $needle) === false ) $missing[] = $needle;
//If the count of $missing and $needles is equal, we know there were no matches, return false..
if (count($missing) == count($needles)) return false;
//If we're here, be happy, return true...
return true;
}
Back to our first example using then the function instead:
$needles = array('.jpg','.png');
if ( !m_strpos( $post['timer_background_image'], $needles ) )
return array("save_data"=>$post,"error"=>array("message"=>"The background image must be in a .jpg or .png format.","field"=>"timer_background_image"));
Of course, what you do after the function returns true or false is up to you.

Answer 4

It seems you are searching for whole words. In this case, something like this might help. As it uses built-in functions, it should be faster than custom code, but you have to profile it:
$words = str_word_count($str, 2);
$word_position_map = array();
foreach($words as $position => $word) {
if(!isset($word_position_map[$word])) {
$word_position_map[$word] = array();
}
$word_position_map[$word][] = $position;
}
// assuming $needles is an array of words
$result = array_intersect_key($word_position_map, array_flip($needles));
Storing the information (like the needles) in the right format will improve the runtime ( e.g. as you don't have to call array_flip).
Note from the str_word_count documentation:
For the purpose of this function, 'word' is defined as a locale dependent string containing alphabetic characters, which also may contain, but not start with "'" and "-" characters.
So make sure you set the locale right.

Answer 5

You could use a regular expression, they support OR operations. This would however make it fairly slow, compared to strpos.

Answer 6

How about a simple solution using array_map()?
$string = 'one two three four';
$needles = array( 'five' , 'three' );
$strpos_arr = array_map( function ( $check ) use ( $string ) {
return strpos( $string, $check );
}, $needles );
As return, you're going to have an array where the keys are the needles positions and the values are the starting positions, if found.
//print_r( $strpos_arr );
Array
(
[0] =>
[1] => 8
)