PHP commonly used array functions (4)

* Array sorting

* Note:

* 1. Arrays are passed by reference, and all original data will be overwritten;

* 2. Array elements It is recommended that all types be the same, otherwise unpredictable results will occur

* 3. Sorting success returns: true, failure returns: false

* Available constants:

* 1.SORT_REGULAR : [Default] Normally compare units (do not change type)

* 2.SORT_NUMERIC: Units are compared as numbers

* 3.SORT_STRING: Units are compared as strings

* 4.SORT_NATURAL: The unit sorts strings in "natural order"

* 5.SORT_FLAG_CASE: Sorts strings case-insensitively

* 1. Positive order: associate (associated), key (key), preceded by the first letters of these two words means

* 1. sort(&$arr, $flag) Arrange in ascending order by value, key name according to index Reset

* 2. asort(&$arr,$flag) Sort by value in ascending order, key name retains correspondence with value

* 3. ksort(&$arr,$flag) Sort by key name in ascending order, suitable for associative arrays, the key-value correspondence remains unchanged

* 2. Reverse order: reversal, just add an r before the function

* 1. rsort( &$arr, $flag): Reverse sort the array

* 2. arsort(&$arr, $flag): Reverse sort the array and maintain the index relationship

* 3. krsort (&$arr, $flag): Sort the array in reverse order by key name

* 3. Customize the callback function to sort: usort(&$arr, functoin($a, $b){ #code } )

* Note: Only sort the values, ignore the key name (that is, the key name will be reset)

$arr = ['id'=>3, 'name'=>'zhu', 'course'=>'php', 'grade'=>60, 5=>true];
echo &#39;<pre class="brush:php;toolbar:false">&#39;;
echo &#39;<p>原始数组:</p>&#39;;
print_r($arr);
echo &#39;<hr color="red">&#39;;

//Here is a very simple example, more complex cases will Introduced in actual combat

$arr1 = [10, 4, 22, 99, 35, 18];

//Now we use the custom callback method to arrange $arr1 from small to large

usort($arr1, function($a, $b) {
$res = $a - $b; 
if ($res == 0) {
return 0;
} else if ($res > 0) {
return true;
} else {
return false;
}
});
print_r($arr1);