b1919676 b1919676 - 1 year ago 69
PHP Question

Reorder array items depending on substring representing time in php

Hi buddies :) I'm required to reorder an array which contains several items with a given format. For example, like this:


As we can see, any item's given format is a string like x=whateverinitialhour_whateverfinalhour

As stated before, I have to reorder these items depending on initial hour, so the expected result should be:


Well, I have been searching a lot and found usort, and I found similar questions too like How to sort multidimensional PHP array (recent news time based implementation)

So, I'm coding this:

$arr = array();
$newarr = array();
$arr = ('m=11:00_12:00','d=10:00_10:30','a=13:00_13:30');
usort($arr, function($a,$b) {return strtotime(substr($a[0],2,5))-strtotime(substr($b[0],2,5));});
foreach ($arr as $value) {
$newarr[] = $value;

Unfortunately, I'm not getting the expected result, and the new array contains this:


Which it is not reordered by every item's initial hour :(

What am I doing wrong? Am I not using usort in a rigth way? Thanks.

Answer Source

Look at your usort() function,

usort($arr, function($a,$b) {
    return strtotime(substr($a[0],2,5))-strtotime(substr($b[0],2,5));
                            ^^^^^                        ^^^^^

$a and $b are not arrays, they are elements of the array. Also, you don't need a new array to store the sorted array, usort() applies the manipulation in the original array itself. So your code should be like this:

$arr = array('m=11:00_12:00','d=10:00_10:30','a=13:00_13:30');
usort($arr, function($a,$b){ 
    return (strtotime(substr($a,2,5)) < strtotime(substr($b,2,5))) ? -1 : 1; 

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