PHP count of occurrences of characters of a string within another string - php

Question

Let's say I have two strings.
$needle = 'AGUXYZ';
$haystack = 'Agriculture ID XYZ-A';
I want to count how often characters that are in $needle occur in $haystack. In $haystack, there are the characters 'A' (twice), 'X', 'Y' and 'Z', all of which are in the needle, thus the result is supposed to be 5 (case-sensitive).
Is there any function for that in PHP or do I have to program it myself?
Thanks in advance!

Answer 1

You can calculate the length of the original string and the length of the string without these characters. The differences between them is the number of matches.
Basically,
$needle = 'AGUXYZ';
$haystack = 'Agriculture ID XYZ-A';
Here is the part that does the work. In one line.
$count = strlen($haystack) - strlen(str_replace(str_split($needle), '', $haystack));
Explanation: The first part is self-explanatory. The second part is the length of the string without the characters in the $needle string. This is done by replacing each occurrences of any characters inside the $needle with a blank string.
To do this, we split $needle into an array, once character for each item, using str_split. Then pass it to str_replace. It replaces each occurence of any items in the $search array with a blank string.
Echo it out,
echo "Count = $count\n";
you get:
Count = 5

Answer 2

Try this;
function count_occurences($char_string, $haystack, $case_sensitive = true){
if($case_sensitive === false){
$char_string = strtolower($char_string);
$haystack = strtolower($haystack);
}
$characters = str_split($char_string);
$character_count = 0;
foreach($characters as $character){
$character_count = $character_count + substr_count($haystack, $character);
}
return $character_count;
}
To use;
$needle = 'AGUXYZ';
$haystack = 'Agriculture ID XYZ-A';
print count_occurences($needle, $haystack);
You can set the third parameter to false to ignore case.

Answer 3

There's no built-in function that handles character sets, but you simply use the substr_count function in a loop as such:
<?php
$sourceCharacters = str_split('AGUXYZ');
$targetString = 'Agriculture ID XYZ-A';
$occurrenceCount = array();
foreach($sourceCharacters as $currentCharacter) {
$occurrenceCount[$currentCharacter] = substr_count($targetString, $currentCharacter);
}
print_r($occurrenceCount);
?>

Answer 4

There is no specific method to do this, but this built in method can surely help you:
$count = substr_count($haystack , $needle);
edit: I just reported the general substr_count method..in your particular case you need to call it for each character inside $needle (thanks #Alan Whitelaw)

Answer 5

If you are not interested in the character distribution, you could use a Regex
echo preg_match_all("/[$needle]/", $haystack, $matches);
which returns the number of full pattern matches (which might be zero), or FALSE if an error occurred. The solution offered by #thai above should be significantly faster though.
If the character distribution is of any importance, you can use count_chars:
$needle = 'AGUXYZ';
$haystack = 'Agriculture ID XYZ-A';
$occurences = array_intersect_key(
count_chars($haystack, 1),
array_flip(
array_map('ord', str_split($needle))
)
);
The result would be an array with keys being the ASCII values of the character.
You can then iterate over it with
foreach($occurences as $char => $amount) {
printf("There is %d occurences of %s\n", $amount, chr($char));
}
You could still pass the $occurences array to array_sum to calculate the total.

Answer 6

substr_count will get you close. However, it will not do individual characters. So you could loop over each character in $needle and call this function while summing the counts.

Answer 7

There is a PHP function substr_count to count the number of instances of a character in a string. It would be trivial to extend it for multiple characters:
function substr_multi_count ($haystack, $needle, $offset = 0, $length = null) {
$ret = 0;
if ($length === null) {
$length = strlen($haystack) - $offset;
}
for ($i = strlen($needle); $i--; ) {
$ret += substr_count($haystack, $needle, $offset, $length);
}
return $ret;
}

Answer 8

I have a recursive method to overcome this:
function countChar($str){
if(strlen($str) == 0) return 0;
if(substr($str,-1) == "x") return 1 + countChar(substr($str,0,-1));
return 0 + countChar(substr($str,0,-1));
}
echo countChar("xxSR"); // 2
echo countChar("SR"); // 0
echo countChar("xrxrpxxx"); // 5

Answer 9

I'd do something like:
split the string to chars (str_split), and then
use array_count_values to get an array of characters with the respective number of occurrences.
Code:
$needle = 'AGUXYZ';
$string = "asdasdadas asdadas asd asdsd";
$array_chars = str_split($string);
$value_count = array_count_values($array_chars);
for ($i = 0; $i < count($needle); $i++)
echo $needle[$i]. " is occur " .
($value_count[$needle[$i]] ? $value_count[$needle[$i]] : '0')." times";