Find all the occurrence points of a letter within a string - php

Question

I have the following code:
<?php
$word = "aeagle";
$letter = "e";
$array = strposall($aegle, $letter);
print_r($array);
function strposall($haystack, $needle) {
$occurrence_points = array();
$pos = strpos($haystack, $needle);
if ($pos !== false) {
array_push($occurrence_points, $pos);
}
while ($pos = strpos($haystack, $needle, $pos + 1)) {
array_push($occurrence_points, $pos);
}
return $occurrence_points;
}
?>
As in the example, if I have aegle as my word and I'm searching for e within it, the function should return an array with the values 1 and 4 in it.
What's wrong with my code?

Answer 1

Why not trying instead
$word = "aeagle";
$letter = "e";
$occurrence_points = array_keys(array_intersect(str_split($word), array($letter)));
var_dump($occurrence_points);

Answer 2

I think you're passing the wrong parameters, shouild be $word instead of $aegle

Answer 3

Little bit more literal than the other answer:
function charpos($str, $char) {
$i = 0;
$pos = 0;
$matches = array();
if (strpos($str, $char) === false) {
return false;
}
while (!!$str) {
$pos = strpos($str, $char);
if ($pos === false) {
$str = '';
} else {
$i = $i + $pos;
$str = substr($str, $pos + 1);
array_push($matches, $i++);
}
}
return $matches;
}
https://ignite.io/code/511ff26eec221e0741000000
Using:
$str = 'abc is the place to be heard';
$positions = charpos($str, 'a');
print_r($positions);
while ($positions) {
$i = array_shift($positions);
echo "$i: $str[$i]\n";
}
Which gives:
Array (
[0] => 0
[1] => 13
[2] => 25
)
0: a
13: a
25: a

Answer 4

Other's have pointed out you're passing the wrong parameters. But you're also reinventing the wheel. Take a look at php's regular expression match-all (whoops, had linked the wrong function), it will already return an array of all matches with offsets, when used with the following flag.
flags
flags can be the following flag:
PREG_OFFSET_CAPTURE
If this flag is passed, for every occurring match the appendant string offset will also be returned. Note that this changes the value of matches into an array where every element is an array consisting of the matched string at offset 0 and its string offset into subject at offset 1.
Use a single letter pattern for the search term $letter = '/e/' and you should get back an array with all your positions as the second element of each result array, which you can then finagle into the output format you're looking for.
Update: Jared points out that you do get the capture of the pattern back, but with the flag set, you also get the offset. As a direct answer to the OP's question, try this code:
$word = "aeagle";
$pattern = "/e/";
$matches = array();
preg_match_all($pattern, $word, $matches, PREG_OFFSET_CAPTURE);
print_r($matches);
It has the following ouput:
Array
(
// Matches of the first pattern: /e/
[0] => Array
(
// First match
[0] => Array
(
// Substring of $word that matched
[0] => e
// Offset into $word where previous substring starts
[1] => 1
)
[1] => Array
(
[0] => e
[1] => 5
)
)
)
The results are 3D instead of 2D because preg_match_all can match multiple patterns at once. The hits are for the first (and in this case: only) pattern supplied and are thus in the first array.
And unlike the OP originally stated, 1 and 5 are the correct indexes of the letter e in the string 'aeagle'
aeagle
012345
^ ^
1 5
Performance wise, the customized version of strposall would probably be faster than a regular expression match. But learning to use an in-built function is almost always faster than developing, testing, supporting and maintaining your own code. And 9 times out of 10, that's the most expensive part of programming.