Interpreting PHP array sorting

PHP has a set of powerful function libraries. Let’s take a look at the specific usage of each array sorting function. The screenshots below are from the PHP7.0 manual.

• sort( ) — Sort the array from low to high. This function is the root function of all sorting functions; bool sort ( array &$array [, int $sort_flags = SORT_REGULAR ] )Two parameters, in addition to the array, the second optional parameter sort_flags changes the sorting through optional type flags Behavior.

<code><span><span><?php</span><span>$auto</span> = <span>array</span>(<span>"bens2"</span>,<span>"honda3"</span>,<span>"BMW4"</span>,<span>"aens1"</span>,<span>"BMW5"</span>);
sort(<span>$auto</span>,SORT_STRING|SORT_FLAG_CASE);<span>//不区分大小写排序字符串</span><span>foreach</span>(<span>$auto</span><span>as</span><span>$key</span>=><span>$val</span>)
{
    <span>echo</span><span>"auto["</span>.<span>$key</span>.<span>"]="</span>.<span>$val</span>.<span>"\n"</span>;
    <span>//输出auto[0]=BMW4 auto[1]=BMW5 auto[2]=aens1 auto[3]=bens2 auto[4]=honda3</span>
}</span></span></code>

• rsort — Sort the array in reverse, the parameter list is the same as sort, and the return value is the same as

<code><span><span><?php</span><span>$auto</span> = <span>array</span>(<span>"bens2"</span>,<span>"honda3"</span>,<span>"BMW4"</span>,<span>"aens1"</span>,<span>"BMW5"</span>);
rsort(<span>$auto</span>,SORT_STRING|SORT_FLAG_CASE);<span>//不区分大小写排序字符串</span><span>foreach</span>(<span>$auto</span><span>as</span><span>$key</span>=><span>$val</span>)
{
    <span>echo</span><span>"auto["</span>.<span>$key</span>.<span>"]="</span>.<span>$val</span>.<span>"\n"</span>;
    <span>//输出auto[0]=honda3 auto[1]=BMW5 auto[2]=BMW4 auto[3]=bens2 auto[4]=aens1</span>
}</span></span></code>

• asort() — Sort the array and maintain the index relationship, the parameters and return value are the same as above, the explanation in the manual is "This function sorts the array, and the index of the array remains associated with the unit. It is mainly used to sort associative arrays where the order of the units is important." Personally, I think it and sort() focus on sorting associative arrays. Simply put, the sorting rules are based on values, not keys. This is easily distinguished from ksort().

<code><span><span><?php</span><span>$auto</span> = <span>array</span>(<span>"a"</span>=><span>"bens2"</span>,<span>"b"</span>=><span>"honda3"</span>,<span>"c"</span>=><span>"BMW4"</span>,<span>"d"</span>=><span>"aens1"</span>,<span>"e"</span>=><span>"BMW5"</span>);
asort(<span>$auto</span>,SORT_STRING|SORT_FLAG_CASE);<span>//不区分大小写排序字符串</span><span>foreach</span>(<span>$auto</span><span>as</span><span>$key</span>=><span>$val</span>)
{
    <span>echo</span><span>"auto["</span>.<span>$key</span>.<span>"]="</span>.<span>$val</span>.<span>"\n"</span>;
    <span>//输出auto[d]=aens1 auto[a]=bens2 auto[c]=BMW4 auto[e]=BMW5 auto[b]=honda3</span>
}</span></span></code>

• arsort() — Reverse sort the array and maintain index relationship, it is the inverse sort of asort().

<code><span><span><?php</span><span>$auto</span> = <span>array</span>(<span>"a"</span>=><span>"bens2"</span>,<span>"b"</span>=><span>"honda3"</span>,<span>"c"</span>=><span>"BMW4"</span>,<span>"d"</span>=><span>"aens1"</span>,<span>"e"</span>=><span>"BMW5"</span>);
arsort(<span>$auto</span>,SORT_STRING|SORT_FLAG_CASE);<span>//不区分大小写排序字符串</span><span>foreach</span>(<span>$auto</span><span>as</span><span>$key</span>=><span>$val</span>)
{
    <span>echo</span><span>"auto["</span>.<span>$key</span>.<span>"]="</span>.<span>$val</span>.<span>"\n"</span>;
    <span>//输出auto[b]=honda3 auto[e]=BMW5 auto[c]=BMW4 auto[a]=bens2 auto[d]=aens1</span>
}</span></span></code>

• ksort() - Sort the array by key name. The manual explains that "sort the array by key name and retain the association between key name and data. This function is mainly used for associative arrays." The parameters and return value are the same as sort ()

<code><span><span><?php</span><span>$auto</span> = <span>array</span>(<span>"b"</span>=><span>"bens2"</span>,<span>"a"</span>=><span>"honda3"</span>,<span>"d"</span>=><span>"BMW4"</span>,<span>"c"</span>=><span>"aens1"</span>,<span>"e"</span>=><span>"BMW5"</span>);
ksort(<span>$auto</span>,SORT_STRING|SORT_FLAG_CASE);<span>//不区分大小写排序字符串</span><span>foreach</span>(<span>$auto</span><span>as</span><span>$key</span>=><span>$val</span>)
{
    <span>echo</span><span>"auto["</span>.<span>$key</span>.<span>"]="</span>.<span>$val</span>.<span>"\n"</span>;
    <span>//输出auto[a]=honda3 auto[b]=bens2 auto[c]=aens1 auto[d]=BMW4 auto[e]=BMW5</span>
}</span></span></code>

• krsort — Sort the array in reverse order by key name. The parameters and return values ​​are the same as above.

<code><span><span><?php</span><span>$auto</span> = <span>array</span>(<span>"b"</span>=><span>"bens2"</span>,<span>"a"</span>=><span>"honda3"</span>,<span>"d"</span>=><span>"BMW4"</span>,<span>"c"</span>=><span>"aens1"</span>,<span>"e"</span>=><span>"BMW5"</span>);
ksort(<span>$auto</span>,SORT_STRING|SORT_FLAG_CASE);<span>//不区分大小写排序字符串</span><span>foreach</span>(<span>$auto</span><span>as</span><span>$key</span>=><span>$val</span>)
{
    <span>echo</span><span>"auto["</span>.<span>$key</span>.<span>"]="</span>.<span>$val</span>.<span>"\n"</span>;
    <span>//输出auto[a]=honda3 auto[b]=bens2 auto[c]=aens1 auto[d]=BMW4 auto[e]=BMW5</span>
}</span></span></code>

• natsort — Use the "natural sorting" algorithm to sort the array. The manual explains that "This function implements a sum People usually sort alphanumeric strings using the same sorting algorithm and retaining the original key/value association. This is called "natural sorting" and is different from the sorting method of sort() which takes only one parameter. That is, the parameters passed in.

• <code><span><span><?php</span><span>$auto</span> = <span>array</span>(<span>"b"</span>=><span>"bens2"</span>,<span>"e"</span>=><span>"bens20"</span>,<span>"a"</span>=><span>"bens31"</span>,<span>"d"</span>=><span>"bens41"</span>,<span>"c"</span>=><span>"bens1"</span>,<span>"e"</span>=><span>"bens15"</span>);
  sort(<span>$auto</span>,SORT_STRING|SORT_FLAG_CASE);<span>//不区分大小写排序字符串</span><span>echo</span><span>"sort排序：<br>"</span>;
  <span>foreach</span>(<span>$auto</span><span>as</span><span>$key</span>=><span>$val</span>)
  {
      <span>echo</span><span>"auto["</span>.<span>$key</span>.<span>"]="</span>.<span>$val</span>.<span>"<br>"</span>;
  
  }
  <span>$auto1</span> = <span>array</span>(<span>"b"</span>=><span>"bens2"</span>,<span>"e"</span>=><span>"bens20"</span>,<span>"a"</span>=><span>"bens31"</span>,<span>"d"</span>=><span>"bens41"</span>,<span>"c"</span>=><span>"bens1"</span>,<span>"e"</span>=><span>"bens15"</span>);
  natsort(<span>$auto1</span>);<span>//参数只有一个</span><span>echo</span><span>"natsort排序：<br>"</span>;
  <span>foreach</span>(<span>$auto1</span><span>as</span><span>$key</span>=><span>$val</span>)
  {
      <span>echo</span><span>"auto["</span>.<span>$key</span>.<span>"]="</span>.<span>$val</span>.<span>"<br>"</span>;
  
  }
  <span>//输出</span><span>/* sort排序：
  auto[0]=bens1
  auto[1]=bens15
  auto[2]=bens2
  auto[3]=bens31
  auto[4]=bens41
  natsort排序：
  auto[c]=bens1
  auto[b]=bens2
  auto[e]=bens15
  auto[a]=bens31
  auto[d]=bens41 */</span></span></span></code>

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