Peek ahead when iterating an array of arrays in PHP - php

Question

I have a mysql query object result which I want to parse through. Let's say the array looks like this.
$superheroes = array(
[0] => array(
"name" => "Peter Parker",
"email" => "peterparker#mail.com",
"age"=>"33",
"sex"=>"male",
),
[1] => array(
"name" => "jLaw",
"email" => "jlaw#mail.com",
"age"=>"22",
"sex"=>"female",
),
[2] => array(
"name" => "Clark Kent",
"email" => "clarkkent#mail.com",
"age"=>"36",
"sex"=>"male",
),
[3] => array(
"name" => "Gal Gadot",
"email" => "gal#mail.com",
"age"=>"22",
"sex"=>"female",
)
);
I want to iterate through this array, and while I am at each array, I want to look ahead in the next array, and find out the age difference between current male hero and next immediate female in the list. I found a lot of posts that talk about
1. array_keys
2. caching iterators,
3. prev, next, etc.
But all of them are talking about one dimensional arrays. Here Is what I tried
foreach ($superheroes as $key => $list){
if($list['sex']=="male"){
$currentHerosAge=$list['age'];
while($next=next($superheroes)){
if($next['sex']=="female"){
$diff=$currentHerosAge -$next['age'];
echo "Age diff: ".$diff;
break;
}
}
}
}
But when I try this, for array[0], next misses the array[1], and picks up array[3]. Not sure how to work this out.

Answer 1

You can use array_slice to slice array form the next key index and then look for the fist female age
$diff = [];
foreach($superheroes as $key => $male) {
if ($male['sex'] === 'female' ) continue;
// get the next key index
$nextKey = $key + 1;
if ( isset( $superheroes[ $nextKey ] ) ) {
// slice from the next key index
$nextSuperHeros = array_slice($superheroes, $nextKey);
foreach($nextSuperHeros as $k => $female) {
if ($female['sex'] === 'female') {
$diff[] = $male['age'] - $female['age'];
break;
}
}
}
}
A working Example
Hope this helps

Answer 2

Normally, you don't use a "lookahead", when iterating over the array. The common way would be to store the item of the last iteration and do the comparison on this element
$last_hero = false;
foreach ($superheroes as $hero) {
if ($last_hero) {
// do some stuff..
}
$last_hero = $hero;
}
If you really need a lookahead of more than one item, you wouldn't use a foreach loop.
for ($i = 0; $i < count($superheroes); $i++) {
// do sth. with $superheroes[$i]
if (...) {
for ($j = $i + 1; $j < count($superheroes); $j++) {
// do sth. with $superheroes[$j]
}
}
}

Answer 3

this code works, here's your solution for that situation (i will update explaining why) + editing the Clark - Gal part, one more comparison.
Execute it here if you like. this is a fancy version with echo's just to illustrate the running logic and what is happening inside the loops :) of course the final result can be much more simple.
<?php
$superheroes = [
[
"name" = "Peter Parker",
"email" = "peterparker#mail.com",
"age"="33",
"sex"="male",
],[
"name" = "jLaw",
"email" = "jlaw#mail.com",
"age"="22",
"sex"="female",
],[
"name" = "Clark Kent",
"email" = "clarkkent#mail.com",
"age"="36",
"sex"="male",
],[
"name" = "Gal Gadot",
"email" = "gal#mail.com",
"age"="22",
"sex"="female",
]
];
$length = count($superheroes);
$counterReset = 0;
while ($current = current($superheroes) )
{
$length -= 1;
if($current['sex']=="male"){
$currentHerosAge = $current['age'];
while($next = next($superheroes)){
$counterReset += 1;
if($next['sex']=="female"){
$diff=$currentHerosAge - $next['age'];
echo "\n C: ".$current['name']." to ".$next['name']." Age diff: ".$diff."\n";
break;
}
}
}
if($counterReset 0){
for($i = 0; $i < $counterReset; $i++){
prev($superheroes);
}
$counterReset = 0;
}
if($length == 0){
break;
}
next($superheroes);
}
current() next() prev() all act as pointers. Which means that every time you call them you control the movement of the assuming "head" of array or element you are calling. For this reason every time you move with next() you must make sure you also return back to the desired position in order to continue looping the regular loop :)
References next(), current(), prev() and reset()
execution logic
You declaration of the array or arrays was bringing a PHP Warning PHP Warning: Illegal offset type in /home/ on line 21 and was empty. For that reason I re-declared that way.