all positions of a needle

[Anon]

Hi!

Looking for an algorithm to find all positions of a needle in the haystack. strpos finds only position of the first occurrence.

Can anybody help?
Bye

[Anon]

Hi Dado,

How about this:

$needle = "abc";
$haystack = "abcdacbasdasllaabc";
$len_string = strlen($haystack);
$j = 0;

for ($i=0;$i<$len_string;$i) {
if ($result = strpos($needle, $haystack, $i)) {
$res_array[$j] = $result;
$i = $result + 1;
$j++;
}
}

Explanation:

The for statement searches for the $needle as many times are there are characters in the $haystack. If the string is found (giving the position), the position is added to the $res_array as a numerated array. Also, the for statement variable, $i, is advanced (to prevent duplicated results) to the character after the position where the $needle was found. $j is incremented to increase the array number.

To find the number of successful occurances, use count($res_array).

Kind Regards,

~D.

[[deleted]]

the idea for that piece of code is ok, but the code itself is bad.. quite bad. :-)

Try this function, as copied from the annotations in the manual:

function occurances($needle, $haystack) {
while (strpos($haystack, $needle, $last) !== false) {
$i[] = strpos($haystack, $needle, $last);
$last = $i[count($i) - 1] + 1;
}
return $i;
}

[Anon]

Vincent,

Give me a break! It works.. :-)

-D.

[[deleted]]

Hehe... the principal works, you script doesn't ;-)

You reversed the needle and the haystack, and your function doesn't
account for the case where the needle occurs at position zero in the haystack.

other than that it's cute. :-)

[Anon]

Vincent,

Back to that "Hello World!" script, then.. :-)

Cheers,

-D.

[[deleted]]

hehe... PHP is fun isn't it? 🙂