How to find a position of character in a string in PHP without using strpos function

 Here we figure out how to perform strpos() function works to find out the first occurrence of any words in a string, but the condition was that do not use strpos() then how to do those things without it.

If you are trying to figure out how something like strpos() could work behind the scenes, here is a very basic example that only uses basic language.

function custom_strpos ($haystack, $needle, $offset = 0) {

    // for loop with indexes for both strings, up to the length of $haystack
    for ($h_index=$offset, $n_index=0; isset($haystack[$h_index]); $h_index++, $n_index++) {

        if ($haystack[$h_index] == $needle[$n_index]) {           // *CHARACTERS MATCH*

            if (!isset($start_pos)) $start_pos = $h_index;        // set start_pos if not set

            if (!isset($needle[$n_index + 1])) return $start_pos; // all characters match


        } else {                                                  // *CHARACTERS DON'T MATCH*

            $n_index = -1;                                        // reset $needle index

            unset($start_pos);                                    // unset match start pos.
        }
    }
    // all charactes of $haystack iterated without matching $needle
    return false;
}

This is the native implementation for strpos alternatives.

If you want to understand strpos does work behind the scenes here is s a great article about how to understand the PHP source of any functions.

Also, you can use another alternatives function rather than strpos, like strstr function, this function also works similarly.

<?php 
   $str = "How are you?";
   $find = "are";
// Returns false if given words is not inside string
   strstr($str, $find);
?>